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	$48.30	9.469%	$52.8735	$52.87	$52.85	$52.90
Purchase #2	$177.52	4.555%	$185.606	$185.61	$185.60	$185.60
Purchase #3	$105.39	4.544%	$110.1789	$110.18	$110.20	$110.20
Purchase #4	$191.29	10.516%	$211.4061	$211.41	$211.40	$211.40
Purchase #5	$209.87	6.552%	$223.6207	$223.62	$223.60	$223.60
Purchase #6	$212.33	12.248%	$238.3362	$238.34	$238.35	$238.30
Purchase #7	$29.41	13.676%	$33.4321	$33.43	$33.45	$33.40
7 purchase totals =	$974.11		$1,055.4535	$1,055.46	$1,055.45	$1,055.40