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	$218.75	11.150%	$243.1406	$243.14	$243.15	$243.10
Purchase #2	$92.53	13.707%	$105.2131	$105.21	$105.20	$105.20
Purchase #3	$45.86	11.850%	$51.2944	$51.29	$51.30	$51.30
Purchase #4	$158.64	3.657%	$164.4415	$164.44	$164.45	$164.40
Purchase #5	$78.57	5.302%	$82.7358	$82.74	$82.75	$82.70
Purchase #6	$109.72	8.154%	$118.6666	$118.67	$118.65	$118.70
Purchase #7	$100.32	10.692%	$111.0462	$111.05	$111.05	$111.00
7 purchase totals =	$804.39		$876.5382	$876.54	$876.55	$876.40