Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$114.84	11.326%	$127.8468	$127.85	$127.85	$127.80
Purchase #2	$241.86	13.458%	$274.4095	$274.41	$274.40	$274.40
Purchase #3	$134.75	5.245%	$141.8176	$141.82	$141.80	$141.80
Purchase #4	$107.85	12.116%	$120.9171	$120.92	$120.90	$120.90
Purchase #5	$138.69	13.609%	$157.5643	$157.56	$157.55	$157.60
Purchase #6	$184.35	13.820%	$209.8272	$209.83	$209.85	$209.80
Purchase #7	$237.92	13.315%	$269.599	$269.60	$269.60	$269.60
7 purchase totals =	$1,160.26		$1,301.9815	$1,301.99	$1,301.95	$1,301.90