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	$47.27	12.102%	$52.9906	$52.99	$53.00	$53.00
Purchase #2	$21.81	10.618%	$24.1258	$24.13	$24.15	$24.10
Purchase #3	$32.55	3.106%	$33.561	$33.56	$33.55	$33.60
Purchase #4	$106.76	5.173%	$112.2827	$112.28	$112.30	$112.30
Purchase #5	$151.32	4.162%	$157.6179	$157.62	$157.60	$157.60
Purchase #6	$29.67	6.104%	$31.4811	$31.48	$31.50	$31.50
Purchase #7	$86.96	5.158%	$91.4454	$91.45	$91.45	$91.40
7 purchase totals =	$476.34		$503.5045	$503.51	$503.55	$503.50