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	$172.43	5.569%	$182.0326	$182.03	$182.05	$182.00
Purchase #2	$33.76	4.776%	$35.3724	$35.37	$35.35	$35.40
Purchase #3	$22.64	6.652%	$24.146	$24.15	$24.15	$24.10
Purchase #4	$243.69	5.111%	$256.145	$256.15	$256.15	$256.10
Purchase #5	$224.95	8.136%	$243.2519	$243.25	$243.25	$243.30
Purchase #6	$55.42	5.628%	$58.539	$58.54	$58.55	$58.50
Purchase #7	$48.42	7.147%	$51.8806	$51.88	$51.90	$51.90
7 purchase totals =	$801.31		$851.3675	$851.37	$851.40	$851.30