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	$155.26	11.521%	$173.1475	$173.15	$173.15	$173.10
Purchase #2	$243.54	4.519%	$254.5456	$254.55	$254.55	$254.50
Purchase #3	$85.40	4.238%	$89.0193	$89.02	$89.00	$89.00
Purchase #4	$150.40	6.547%	$160.2467	$160.25	$160.25	$160.20
Purchase #5	$22.84	10.713%	$25.2868	$25.29	$25.30	$25.30
Purchase #6	$197.54	6.627%	$210.631	$210.63	$210.65	$210.60
Purchase #7	$162.61	5.600%	$171.7162	$171.72	$171.70	$171.70
7 purchase totals =	$1,017.59		$1,084.5931	$1,084.61	$1,084.60	$1,084.40