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	$216.46	12.443%	$243.3941	$243.39	$243.40	$243.40
Purchase #2	$227.56	7.683%	$245.0434	$245.04	$245.05	$245.00
Purchase #3	$28.91	12.277%	$32.4593	$32.46	$32.45	$32.50
Purchase #4	$147.89	5.518%	$156.0506	$156.05	$156.05	$156.10
Purchase #5	$197.56	12.485%	$222.2254	$222.23	$222.25	$222.20
Purchase #6	$11.28	3.561%	$11.6817	$11.68	$11.70	$11.70
Purchase #7	$115.95	10.676%	$128.3288	$128.33	$128.35	$128.30
7 purchase totals =	$945.61		$1,039.1833	$1,039.18	$1,039.25	$1,039.20