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	$42.48	8.422%	$46.0577	$46.06	$46.05	$46.10
Purchase #2	$40.59	5.796%	$42.9426	$42.94	$42.95	$42.90
Purchase #3	$40.42	9.770%	$44.369	$44.37	$44.35	$44.40
Purchase #4	$223.94	9.746%	$245.7652	$245.77	$245.75	$245.80
Purchase #5	$79.60	7.397%	$85.488	$85.49	$85.50	$85.50
Purchase #6	$132.35	13.580%	$150.3231	$150.32	$150.30	$150.30
Purchase #7	$64.79	3.708%	$67.1924	$67.19	$67.20	$67.20
7 purchase totals =	$624.17		$682.1380	$682.14	$682.10	$682.20