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	$210.31	13.219%	$238.1109	$238.11	$238.10	$238.10
Purchase #2	$28.64	8.804%	$31.1615	$31.16	$31.15	$31.20
Purchase #3	$179.77	8.705%	$195.419	$195.42	$195.40	$195.40
Purchase #4	$46.60	13.507%	$52.8943	$52.89	$52.90	$52.90
Purchase #5	$64.72	9.152%	$70.6432	$70.64	$70.65	$70.60
Purchase #6	$161.95	10.268%	$178.579	$178.58	$178.60	$178.60
Purchase #7	$34.44	9.168%	$37.5975	$37.60	$37.60	$37.60
7 purchase totals =	$726.43		$804.4054	$804.40	$804.40	$804.40