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	$165.34	13.351%	$187.4145	$187.41	$187.40	$187.40
Purchase #2	$84.47	8.265%	$91.4514	$91.45	$91.45	$91.50
Purchase #3	$241.61	6.748%	$257.9138	$257.91	$257.90	$257.90
Purchase #4	$226.84	10.597%	$250.8782	$250.88	$250.90	$250.90
Purchase #5	$36.89	4.371%	$38.5025	$38.50	$38.50	$38.50
Purchase #6	$228.75	5.744%	$241.8894	$241.89	$241.90	$241.90
Purchase #7	$43.39	12.477%	$48.8038	$48.80	$48.80	$48.80
7 purchase totals =	$1,027.29		$1,116.8536	$1,116.84	$1,116.85	$1,116.90