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	$35.72	5.175%	$37.5685	$37.57	$37.55	$37.60
Purchase #2	$210.85	8.187%	$228.1123	$228.11	$228.10	$228.10
Purchase #3	$54.46	6.302%	$57.8921	$57.89	$57.90	$57.90
Purchase #4	$124.57	6.178%	$132.2659	$132.27	$132.25	$132.30
Purchase #5	$173.72	6.812%	$185.5538	$185.55	$185.55	$185.60
Purchase #6	$108.36	7.628%	$116.6257	$116.63	$116.65	$116.60
Purchase #7	$48.96	5.622%	$51.7125	$51.71	$51.70	$51.70
7 purchase totals =	$756.64		$809.7308	$809.73	$809.70	$809.80