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	$55.82	11.337%	$62.1483	$62.15	$62.15	$62.10
Purchase #2	$80.93	13.478%	$91.8377	$91.84	$91.85	$91.80
Purchase #3	$61.79	7.837%	$66.6325	$66.63	$66.65	$66.60
Purchase #4	$98.38	7.413%	$105.6729	$105.67	$105.65	$105.70
Purchase #5	$123.72	3.119%	$127.5788	$127.58	$127.60	$127.60
Purchase #6	$236.73	12.397%	$266.0774	$266.08	$266.10	$266.10
Purchase #7	$161.93	11.663%	$180.8159	$180.82	$180.80	$180.80
7 purchase totals =	$819.30		$900.7635	$900.77	$900.80	$900.70