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	$150.69	11.502%	$168.0224	$168.02	$168.00	$168.00
Purchase #2	$215.38	13.159%	$243.7219	$243.72	$243.70	$243.70
Purchase #3	$71.88	4.209%	$74.9054	$74.91	$74.90	$74.90
Purchase #4	$244.63	9.431%	$267.7011	$267.70	$267.70	$267.70
Purchase #5	$149.76	9.868%	$164.5383	$164.54	$164.55	$164.50
Purchase #6	$91.94	9.750%	$100.9042	$100.90	$100.90	$100.90
Purchase #7	$17.52	5.422%	$18.4699	$18.47	$18.45	$18.50
7 purchase totals =	$941.80		$1,038.2632	$1,038.26	$1,038.20	$1,038.20