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	$123.37	9.237%	$134.7657	$134.77	$134.75	$134.80
Purchase #2	$239.90	12.322%	$269.4605	$269.46	$269.45	$269.50
Purchase #3	$90.31	13.700%	$102.6825	$102.68	$102.70	$102.70
Purchase #4	$19.71	4.237%	$20.5451	$20.55	$20.55	$20.50
Purchase #5	$102.73	6.747%	$109.6612	$109.66	$109.65	$109.70
Purchase #6	$104.46	5.569%	$110.2774	$110.28	$110.30	$110.30
Purchase #7	$237.34	10.573%	$262.434	$262.43	$262.45	$262.40
7 purchase totals =	$917.82		$1,009.8264	$1,009.83	$1,009.85	$1,009.90