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	$29.42	12.222%	$33.0157	$33.02	$33.00	$33.00
Purchase #2	$86.54	3.532%	$89.5966	$89.60	$89.60	$89.60
Purchase #3	$71.71	6.311%	$76.2356	$76.24	$76.25	$76.20
Purchase #4	$110.69	13.156%	$125.2524	$125.25	$125.25	$125.30
Purchase #5	$196.53	13.591%	$223.2404	$223.24	$223.25	$223.20
Purchase #6	$78.97	5.450%	$83.2739	$83.27	$83.25	$83.30
Purchase #7	$47.71	10.775%	$52.8508	$52.85	$52.85	$52.90
7 purchase totals =	$621.57		$683.4654	$683.47	$683.45	$683.50