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	$40.97	5.727%	$43.3164	$43.32	$43.30	$43.30
Purchase #2	$87.73	9.366%	$95.9468	$95.95	$95.95	$95.90
Purchase #3	$210.33	3.843%	$218.413	$218.41	$218.40	$218.40
Purchase #4	$179.63	8.795%	$195.4285	$195.43	$195.45	$195.40
Purchase #5	$52.80	13.567%	$59.9634	$59.96	$59.95	$60.00
Purchase #6	$33.91	13.295%	$38.4183	$38.42	$38.40	$38.40
Purchase #7	$78.53	5.747%	$83.0431	$83.04	$83.05	$83.00
7 purchase totals =	$683.90		$734.5295	$734.53	$734.50	$734.40