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	$212.32	5.250%	$223.4668	$223.47	$223.45	$223.50
Purchase #2	$229.84	11.118%	$255.3936	$255.39	$255.40	$255.40
Purchase #3	$58.30	11.685%	$65.1124	$65.11	$65.10	$65.10
Purchase #4	$37.75	3.643%	$39.1252	$39.13	$39.15	$39.10
Purchase #5	$189.82	13.673%	$215.7741	$215.77	$215.75	$215.80
Purchase #6	$71.53	6.228%	$75.9849	$75.98	$76.00	$76.00
Purchase #7	$176.72	6.867%	$188.8554	$188.86	$188.85	$188.90
7 purchase totals =	$976.28		$1,063.7124	$1,063.71	$1,063.70	$1,063.80