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	$166.74	8.828%	$181.4598	$181.46	$181.45	$181.50
Purchase #2	$83.69	8.407%	$90.7258	$90.73	$90.75	$90.70
Purchase #3	$209.84	7.181%	$224.9086	$224.91	$224.90	$224.90
Purchase #4	$92.91	13.335%	$105.2995	$105.30	$105.30	$105.30
Purchase #5	$48.71	7.442%	$52.335	$52.34	$52.35	$52.30
Purchase #6	$72.43	4.330%	$75.5662	$75.57	$75.55	$75.60
Purchase #7	$200.37	10.204%	$220.8158	$220.82	$220.80	$220.80
7 purchase totals =	$874.69		$951.1107	$951.13	$951.10	$951.10