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	$117.91	8.570%	$128.0149	$128.01	$128.00	$128.00
Purchase #2	$114.46	12.678%	$128.9712	$128.97	$128.95	$129.00
Purchase #3	$221.97	4.116%	$231.1063	$231.11	$231.10	$231.10
Purchase #4	$145.57	4.140%	$151.5966	$151.60	$151.60	$151.60
Purchase #5	$160.91	3.528%	$166.5869	$166.59	$166.60	$166.60
Purchase #6	$158.83	9.414%	$173.7823	$173.78	$173.80	$173.80
Purchase #7	$37.46	6.353%	$39.8398	$39.84	$39.85	$39.80
7 purchase totals =	$957.11		$1,019.8980	$1,019.90	$1,019.90	$1,019.90