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	$127.90	7.164%	$137.0628	$137.06	$137.05	$137.10
Purchase #2	$146.58	13.171%	$165.8861	$165.89	$165.90	$165.90
Purchase #3	$246.41	11.258%	$274.1508	$274.15	$274.15	$274.20
Purchase #4	$237.45	11.361%	$264.4267	$264.43	$264.45	$264.40
Purchase #5	$43.86	4.677%	$45.9113	$45.91	$45.90	$45.90
Purchase #6	$239.75	3.830%	$248.9324	$248.93	$248.95	$248.90
Purchase #7	$53.75	10.820%	$59.5658	$59.57	$59.55	$59.60
7 purchase totals =	$1,095.70		$1,195.9359	$1,195.94	$1,195.95	$1,196.00