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	$75.63	13.413%	$85.7743	$85.77	$85.75	$85.80
Purchase #2	$194.56	11.327%	$216.5978	$216.60	$216.60	$216.60
Purchase #3	$174.84	8.730%	$190.1035	$190.10	$190.10	$190.10
Purchase #4	$47.28	7.824%	$50.9792	$50.98	$51.00	$51.00
Purchase #5	$230.61	5.592%	$243.5057	$243.51	$243.50	$243.50
Purchase #6	$245.68	4.232%	$256.0772	$256.08	$256.10	$256.10
Purchase #7	$82.34	3.553%	$85.2655	$85.27	$85.25	$85.30
7 purchase totals =	$1,050.94		$1,128.3032	$1,128.31	$1,128.30	$1,128.40