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	$98.25	13.405%	$111.4204	$111.42	$111.40	$111.40
Purchase #2	$138.82	12.155%	$155.6936	$155.69	$155.70	$155.70
Purchase #3	$34.94	7.144%	$37.4361	$37.44	$37.45	$37.40
Purchase #4	$61.38	4.497%	$64.1403	$64.14	$64.15	$64.10
Purchase #5	$89.41	7.301%	$95.9378	$95.94	$95.95	$95.90
Purchase #6	$91.54	3.817%	$95.0341	$95.03	$95.05	$95.00
Purchase #7	$101.34	6.597%	$108.0254	$108.03	$108.05	$108.00
7 purchase totals =	$615.68		$667.6877	$667.69	$667.75	$667.50