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	$129.61	8.713%	$140.9029	$140.90	$140.90	$140.90
Purchase #2	$55.75	13.748%	$63.4145	$63.41	$63.40	$63.40
Purchase #3	$119.68	6.198%	$127.0978	$127.10	$127.10	$127.10
Purchase #4	$62.43	13.456%	$70.8306	$70.83	$70.85	$70.80
Purchase #5	$137.89	3.251%	$142.3728	$142.37	$142.35	$142.40
Purchase #6	$180.50	13.496%	$204.8603	$204.86	$204.85	$204.90
Purchase #7	$235.28	11.829%	$263.1113	$263.11	$263.10	$263.10
7 purchase totals =	$921.14		$1,012.5902	$1,012.58	$1,012.55	$1,012.60