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	$211.47	12.204%	$237.2778	$237.28	$237.30	$237.30
Purchase #2	$24.26	8.480%	$26.3172	$26.32	$26.30	$26.30
Purchase #3	$61.72	4.644%	$64.5863	$64.59	$64.60	$64.60
Purchase #4	$235.97	12.665%	$265.8556	$265.86	$265.85	$265.90
Purchase #5	$233.71	12.672%	$263.3257	$263.33	$263.35	$263.30
Purchase #6	$97.32	7.869%	$104.9781	$104.98	$105.00	$105.00
Purchase #7	$49.38	11.642%	$55.1288	$55.13	$55.15	$55.10
7 purchase totals =	$913.83		$1,017.4695	$1,017.49	$1,017.55	$1,017.50