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	$40.90	11.573%	$45.6334	$45.63	$45.65	$45.60
Purchase #2	$87.96	12.233%	$98.7201	$98.72	$98.70	$98.70
Purchase #3	$42.69	7.586%	$45.9285	$45.93	$45.95	$45.90
Purchase #4	$219.85	4.287%	$229.275	$229.28	$229.30	$229.30
Purchase #5	$108.31	9.214%	$118.2897	$118.29	$118.30	$118.30
Purchase #6	$21.57	4.622%	$22.567	$22.57	$22.55	$22.60
Purchase #7	$89.41	10.741%	$99.0135	$99.01	$99.00	$99.00
7 purchase totals =	$610.69		$659.4272	$659.43	$659.45	$659.40