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	$53.43	6.206%	$56.7459	$56.75	$56.75	$56.70
Purchase #2	$243.59	11.446%	$271.4713	$271.47	$271.45	$271.50
Purchase #3	$194.66	9.293%	$212.7498	$212.75	$212.75	$212.70
Purchase #4	$6.95	4.362%	$7.2532	$7.25	$7.25	$7.30
Purchase #5	$141.69	3.321%	$146.3955	$146.40	$146.40	$146.40
Purchase #6	$36.53	3.814%	$37.9233	$37.92	$37.90	$37.90
Purchase #7	$235.77	5.782%	$249.4022	$249.40	$249.40	$249.40
7 purchase totals =	$912.62		$981.9412	$981.94	$981.90	$981.90