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	$111.59	7.447%	$119.9001	$119.90	$119.90	$119.90
Purchase #2	$139.47	6.494%	$148.5272	$148.53	$148.55	$148.50
Purchase #3	$221.53	10.244%	$244.2235	$244.22	$244.20	$244.20
Purchase #4	$99.45	12.222%	$111.6048	$111.60	$111.60	$111.60
Purchase #5	$40.72	12.680%	$45.8833	$45.88	$45.90	$45.90
Purchase #6	$234.36	11.519%	$261.3559	$261.36	$261.35	$261.40
Purchase #7	$94.35	4.484%	$98.5807	$98.58	$98.60	$98.60
7 purchase totals =	$941.47		$1,030.0755	$1,030.07	$1,030.10	$1,030.10