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	$64.52	11.758%	$72.1063	$72.11	$72.10	$72.10
Purchase #2	$155.66	6.759%	$166.1811	$166.18	$166.20	$166.20
Purchase #3	$111.97	11.137%	$124.4401	$124.44	$124.45	$124.40
Purchase #4	$204.80	3.121%	$211.1918	$211.19	$211.20	$211.20
Purchase #5	$55.51	10.391%	$61.278	$61.28	$61.30	$61.30
Purchase #6	$225.67	3.481%	$233.5256	$233.53	$233.55	$233.50
Purchase #7	$219.97	10.412%	$242.8733	$242.87	$242.85	$242.90
7 purchase totals =	$1,038.10		$1,111.5962	$1,111.60	$1,111.65	$1,111.60