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	$90.67	4.640%	$94.8771	$94.88	$94.90	$94.90
Purchase #2	$142.26	11.600%	$158.7622	$158.76	$158.75	$158.80
Purchase #3	$244.74	6.811%	$261.4092	$261.41	$261.40	$261.40
Purchase #4	$88.31	3.194%	$91.1306	$91.13	$91.15	$91.10
Purchase #5	$158.59	8.691%	$172.3731	$172.37	$172.35	$172.40
Purchase #6	$28.74	11.574%	$32.0664	$32.07	$32.05	$32.10
Purchase #7	$220.29	10.634%	$243.7156	$243.72	$243.70	$243.70
7 purchase totals =	$973.60		$1,054.3342	$1,054.34	$1,054.30	$1,054.40