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	$43.51	13.544%	$49.403	$49.40	$49.40	$49.40
Purchase #2	$198.95	12.257%	$223.3353	$223.34	$223.35	$223.30
Purchase #3	$35.43	5.354%	$37.3269	$37.33	$37.35	$37.30
Purchase #4	$233.25	4.638%	$244.0681	$244.07	$244.05	$244.10
Purchase #5	$218.43	13.228%	$247.3239	$247.32	$247.30	$247.30
Purchase #6	$58.81	4.378%	$61.3847	$61.38	$61.40	$61.40
Purchase #7	$80.45	6.665%	$85.812	$85.81	$85.80	$85.80
7 purchase totals =	$868.83		$948.6539	$948.65	$948.65	$948.60