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	$185.29	6.255%	$196.8799	$196.88	$196.90	$196.90
Purchase #2	$29.76	5.834%	$31.4962	$31.50	$31.50	$31.50
Purchase #3	$244.82	5.428%	$258.1088	$258.11	$258.10	$258.10
Purchase #4	$172.28	11.562%	$192.199	$192.20	$192.20	$192.20
Purchase #5	$118.79	10.663%	$131.4566	$131.46	$131.45	$131.50
Purchase #6	$152.32	5.148%	$160.1614	$160.16	$160.15	$160.20
Purchase #7	$250.49	13.679%	$284.7545	$284.75	$284.75	$284.80
7 purchase totals =	$1,153.75		$1,255.0564	$1,255.06	$1,255.05	$1,255.20