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	$225.76	10.336%	$249.0946	$249.09	$249.10	$249.10
Purchase #2	$212.33	5.194%	$223.3584	$223.36	$223.35	$223.40
Purchase #3	$78.88	8.675%	$85.7228	$85.72	$85.70	$85.70
Purchase #4	$178.89	13.705%	$203.4069	$203.41	$203.40	$203.40
Purchase #5	$83.40	8.455%	$90.4515	$90.45	$90.45	$90.50
Purchase #6	$105.32	6.214%	$111.8646	$111.86	$111.85	$111.90
Purchase #7	$138.30	7.847%	$149.1524	$149.15	$149.15	$149.20
7 purchase totals =	$1,022.88		$1,113.0512	$1,113.04	$1,113.00	$1,113.20