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	$210.39	5.581%	$222.1319	$222.13	$222.15	$222.10
Purchase #2	$40.34	4.850%	$42.2965	$42.30	$42.30	$42.30
Purchase #3	$222.45	6.508%	$236.927	$236.93	$236.95	$236.90
Purchase #4	$164.98	9.558%	$180.7488	$180.75	$180.75	$180.70
Purchase #5	$42.93	8.548%	$46.5997	$46.60	$46.60	$46.60
Purchase #6	$88.90	3.113%	$91.6675	$91.67	$91.65	$91.70
Purchase #7	$58.47	9.672%	$64.1252	$64.13	$64.15	$64.10
7 purchase totals =	$828.46		$884.4966	$884.51	$884.55	$884.40