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	$229.67	10.315%	$253.3605	$253.36	$253.35	$253.40
Purchase #2	$40.27	7.577%	$43.3213	$43.32	$43.30	$43.30
Purchase #3	$149.86	8.424%	$162.4842	$162.48	$162.50	$162.50
Purchase #4	$132.88	9.476%	$145.4717	$145.47	$145.45	$145.50
Purchase #5	$171.49	10.548%	$189.5788	$189.58	$189.60	$189.60
Purchase #6	$75.88	12.587%	$85.431	$85.43	$85.45	$85.40
Purchase #7	$223.77	6.603%	$238.5455	$238.55	$238.55	$238.50
7 purchase totals =	$1,023.82		$1,118.1930	$1,118.19	$1,118.20	$1,118.20