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	$62.56	3.129%	$64.5175	$64.52	$64.50	$64.50
Purchase #2	$85.70	6.734%	$91.471	$91.47	$91.45	$91.50
Purchase #3	$57.88	13.477%	$65.6805	$65.68	$65.70	$65.70
Purchase #4	$5.73	13.735%	$6.517	$6.52	$6.50	$6.50
Purchase #5	$90.74	3.371%	$93.7988	$93.80	$93.80	$93.80
Purchase #6	$92.60	7.693%	$99.7237	$99.72	$99.70	$99.70
Purchase #7	$54.26	3.819%	$56.3322	$56.33	$56.35	$56.30
7 purchase totals =	$449.47		$478.0407	$478.04	$478.00	$478.00