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	$127.63	3.185%	$131.695	$131.70	$131.70	$131.70
Purchase #2	$180.90	4.325%	$188.7239	$188.72	$188.70	$188.70
Purchase #3	$156.95	12.424%	$176.4495	$176.45	$176.45	$176.40
Purchase #4	$167.42	7.442%	$179.8794	$179.88	$179.90	$179.90
Purchase #5	$233.70	9.788%	$256.5746	$256.57	$256.55	$256.60
Purchase #6	$153.38	9.360%	$167.7364	$167.74	$167.75	$167.70
Purchase #7	$54.27	8.873%	$59.0854	$59.09	$59.10	$59.10
7 purchase totals =	$1,074.25		$1,160.1442	$1,160.15	$1,160.15	$1,160.10