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	$117.71	5.143%	$123.7638	$123.76	$123.75	$123.80
Purchase #2	$40.39	6.707%	$43.099	$43.10	$43.10	$43.10
Purchase #3	$36.51	12.635%	$41.123	$41.12	$41.10	$41.10
Purchase #4	$147.94	12.557%	$166.5168	$166.52	$166.50	$166.50
Purchase #5	$144.80	11.714%	$161.7619	$161.76	$161.75	$161.80
Purchase #6	$40.46	11.125%	$44.9612	$44.96	$44.95	$45.00
Purchase #7	$48.46	13.323%	$54.9163	$54.92	$54.90	$54.90
7 purchase totals =	$576.27		$636.1420	$636.14	$636.05	$636.20