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	$217.38	12.615%	$244.8025	$244.80	$244.80	$244.80
Purchase #2	$52.96	6.487%	$56.3955	$56.40	$56.40	$56.40
Purchase #3	$6.54	12.310%	$7.3451	$7.35	$7.35	$7.30
Purchase #4	$74.47	11.532%	$83.0579	$83.06	$83.05	$83.10
Purchase #5	$203.47	9.739%	$223.2859	$223.29	$223.30	$223.30
Purchase #6	$182.50	7.560%	$196.297	$196.30	$196.30	$196.30
Purchase #7	$69.57	6.611%	$74.1693	$74.17	$74.15	$74.20
7 purchase totals =	$806.89		$885.3532	$885.37	$885.35	$885.40