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	$205.79	5.501%	$217.1105	$217.11	$217.10	$217.10
Purchase #2	$85.71	5.747%	$90.6358	$90.64	$90.65	$90.60
Purchase #3	$176.47	13.580%	$200.4346	$200.43	$200.45	$200.40
Purchase #4	$99.69	12.185%	$111.8372	$111.84	$111.85	$111.80
Purchase #5	$82.53	12.739%	$93.0435	$93.04	$93.05	$93.00
Purchase #6	$93.57	6.168%	$99.3414	$99.34	$99.35	$99.30
Purchase #7	$186.63	13.537%	$211.8941	$211.89	$211.90	$211.90
7 purchase totals =	$930.39		$1,024.2971	$1,024.29	$1,024.35	$1,024.10