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	$6.82	4.123%	$7.1012	$7.10	$7.10	$7.10
Purchase #2	$192.91	8.539%	$209.3826	$209.38	$209.40	$209.40
Purchase #3	$172.41	9.106%	$188.1097	$188.11	$188.10	$188.10
Purchase #4	$54.47	5.721%	$57.5862	$57.59	$57.60	$57.60
Purchase #5	$246.30	4.162%	$256.551	$256.55	$256.55	$256.60
Purchase #6	$230.98	12.289%	$259.3651	$259.37	$259.35	$259.40
Purchase #7	$108.83	8.179%	$117.7312	$117.73	$117.75	$117.70
7 purchase totals =	$1,012.72		$1,095.8270	$1,095.83	$1,095.85	$1,095.90