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	$235.64	4.337%	$245.8597	$245.86	$245.85	$245.90
Purchase #2	$82.94	12.515%	$93.3199	$93.32	$93.30	$93.30
Purchase #3	$190.63	12.234%	$213.9517	$213.95	$213.95	$214.00
Purchase #4	$172.90	7.335%	$185.5822	$185.58	$185.60	$185.60
Purchase #5	$62.65	4.118%	$65.2299	$65.23	$65.25	$65.20
Purchase #6	$59.98	8.629%	$65.1557	$65.16	$65.15	$65.20
Purchase #7	$227.79	12.190%	$255.5576	$255.56	$255.55	$255.60
7 purchase totals =	$1,032.53		$1,124.6567	$1,124.66	$1,124.65	$1,124.80