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	$89.73	3.343%	$92.7297	$92.73	$92.75	$92.70
Purchase #2	$66.87	8.128%	$72.3052	$72.31	$72.30	$72.30
Purchase #3	$179.85	6.511%	$191.56	$191.56	$191.55	$191.60
Purchase #4	$230.69	10.310%	$254.4741	$254.47	$254.45	$254.50
Purchase #5	$165.83	13.213%	$187.7411	$187.74	$187.75	$187.70
Purchase #6	$12.63	7.203%	$13.5397	$13.54	$13.55	$13.50
Purchase #7	$7.73	5.180%	$8.1304	$8.13	$8.15	$8.10
7 purchase totals =	$753.33		$820.4802	$820.48	$820.50	$820.40