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	$235.82	6.859%	$251.9949	$251.99	$252.00	$252.00
Purchase #2	$42.70	4.129%	$44.4631	$44.46	$44.45	$44.50
Purchase #3	$170.28	6.596%	$181.5117	$181.51	$181.50	$181.50
Purchase #4	$162.68	6.166%	$172.7108	$172.71	$172.70	$172.70
Purchase #5	$100.68	4.858%	$105.571	$105.57	$105.55	$105.60
Purchase #6	$227.35	3.532%	$235.38	$235.38	$235.40	$235.40
Purchase #7	$165.97	13.811%	$188.8921	$188.89	$188.90	$188.90
7 purchase totals =	$1,105.48		$1,180.5236	$1,180.51	$1,180.50	$1,180.60