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	$191.38	10.276%	$211.0462	$211.05	$211.05	$211.00
Purchase #2	$59.64	11.220%	$66.3316	$66.33	$66.35	$66.30
Purchase #3	$167.71	9.159%	$183.0706	$183.07	$183.05	$183.10
Purchase #4	$80.89	11.378%	$90.0937	$90.09	$90.10	$90.10
Purchase #5	$52.58	8.761%	$57.1865	$57.19	$57.20	$57.20
Purchase #6	$83.58	7.623%	$89.9513	$89.95	$89.95	$90.00
Purchase #7	$235.54	9.616%	$258.1895	$258.19	$258.20	$258.20
7 purchase totals =	$871.32		$955.8694	$955.87	$955.90	$955.90