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	$53.53	12.847%	$60.407	$60.41	$60.40	$60.40
Purchase #2	$170.69	8.742%	$185.6117	$185.61	$185.60	$185.60
Purchase #3	$96.38	12.794%	$108.7109	$108.71	$108.70	$108.70
Purchase #4	$139.65	8.500%	$151.5203	$151.52	$151.50	$151.50
Purchase #5	$162.98	6.614%	$173.7595	$173.76	$173.75	$173.80
Purchase #6	$114.60	7.334%	$123.0048	$123.00	$123.00	$123.00
Purchase #7	$58.68	6.778%	$62.6573	$62.66	$62.65	$62.70
7 purchase totals =	$796.51		$865.6715	$865.67	$865.60	$865.70