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	$239.85	6.281%	$254.915	$254.92	$254.90	$254.90
Purchase #2	$136.42	11.705%	$152.388	$152.39	$152.40	$152.40
Purchase #3	$89.41	10.474%	$98.7748	$98.77	$98.75	$98.80
Purchase #4	$76.32	9.687%	$83.7131	$83.71	$83.70	$83.70
Purchase #5	$91.76	7.360%	$98.5135	$98.51	$98.50	$98.50
Purchase #6	$124.99	4.331%	$130.4033	$130.40	$130.40	$130.40
Purchase #7	$128.47	6.168%	$136.394	$136.39	$136.40	$136.40
7 purchase totals =	$887.22		$955.1017	$955.09	$955.05	$955.10