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	$197.30	13.339%	$223.6178	$223.62	$223.60	$223.60
Purchase #2	$42.35	7.134%	$45.3712	$45.37	$45.35	$45.40
Purchase #3	$221.68	7.721%	$238.7959	$238.80	$238.80	$238.80
Purchase #4	$81.60	9.569%	$89.4083	$89.41	$89.40	$89.40
Purchase #5	$106.89	4.218%	$111.3986	$111.40	$111.40	$111.40
Purchase #6	$242.57	11.226%	$269.8009	$269.80	$269.80	$269.80
Purchase #7	$250.29	9.638%	$274.413	$274.41	$274.40	$274.40
7 purchase totals =	$1,142.68		$1,252.8057	$1,252.81	$1,252.75	$1,252.80