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	$53.87	4.717%	$56.411	$56.41	$56.40	$56.40
Purchase #2	$111.48	10.792%	$123.5109	$123.51	$123.50	$123.50
Purchase #3	$6.93	4.689%	$7.2549	$7.25	$7.25	$7.30
Purchase #4	$68.40	6.219%	$72.6538	$72.65	$72.65	$72.70
Purchase #5	$184.34	12.720%	$207.788	$207.79	$207.80	$207.80
Purchase #6	$184.63	11.306%	$205.5043	$205.50	$205.50	$205.50
Purchase #7	$135.62	12.153%	$152.1019	$152.10	$152.10	$152.10
7 purchase totals =	$745.27		$825.2248	$825.21	$825.20	$825.30