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	$213.54	9.427%	$233.6704	$233.67	$233.65	$233.70
Purchase #2	$196.27	5.549%	$207.161	$207.16	$207.15	$207.20
Purchase #3	$42.98	5.324%	$45.2683	$45.27	$45.25	$45.30
Purchase #4	$141.44	10.220%	$155.8952	$155.90	$155.90	$155.90
Purchase #5	$21.27	7.540%	$22.8738	$22.87	$22.85	$22.90
Purchase #6	$55.89	5.818%	$59.1417	$59.14	$59.15	$59.10
Purchase #7	$160.83	9.531%	$176.1587	$176.16	$176.15	$176.20
7 purchase totals =	$832.22		$900.1691	$900.17	$900.10	$900.30