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	$61.25	3.377%	$63.3184	$63.32	$63.30	$63.30
Purchase #2	$32.26	3.323%	$33.332	$33.33	$33.35	$33.30
Purchase #3	$123.57	5.308%	$130.1291	$130.13	$130.15	$130.10
Purchase #4	$37.31	10.375%	$41.1809	$41.18	$41.20	$41.20
Purchase #5	$147.59	12.793%	$166.4712	$166.47	$166.45	$166.50
Purchase #6	$92.58	4.233%	$96.4989	$96.50	$96.50	$96.50
Purchase #7	$181.82	12.137%	$203.8875	$203.89	$203.90	$203.90
7 purchase totals =	$676.38		$734.8180	$734.82	$734.85	$734.80