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	$193.58	12.138%	$217.0767	$217.08	$217.10	$217.10
Purchase #2	$148.27	12.397%	$166.651	$166.65	$166.65	$166.70
Purchase #3	$32.44	3.461%	$33.5627	$33.56	$33.55	$33.60
Purchase #4	$216.47	10.473%	$239.1409	$239.14	$239.15	$239.10
Purchase #5	$171.79	5.812%	$181.7744	$181.77	$181.75	$181.80
Purchase #6	$229.50	5.257%	$241.5648	$241.56	$241.55	$241.60
Purchase #7	$106.67	9.603%	$116.9135	$116.91	$116.90	$116.90
7 purchase totals =	$1,098.72		$1,196.6840	$1,196.67	$1,196.65	$1,196.80