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	$239.95	7.601%	$258.1886	$258.19	$258.20	$258.20
Purchase #2	$79.92	11.484%	$89.098	$89.10	$89.10	$89.10
Purchase #3	$168.51	9.252%	$184.1005	$184.10	$184.10	$184.10
Purchase #4	$167.83	12.398%	$188.6376	$188.64	$188.65	$188.60
Purchase #5	$56.87	4.431%	$59.3899	$59.39	$59.40	$59.40
Purchase #6	$52.93	11.120%	$58.8158	$58.82	$58.80	$58.80
Purchase #7	$214.79	4.229%	$223.8735	$223.87	$223.85	$223.90
7 purchase totals =	$980.80		$1,062.1039	$1,062.11	$1,062.10	$1,062.10