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	$189.47	3.837%	$196.74	$196.74	$196.75	$196.70
Purchase #2	$133.65	11.305%	$148.7591	$148.76	$148.75	$148.80
Purchase #3	$166.70	3.423%	$172.4061	$172.41	$172.40	$172.40
Purchase #4	$23.82	4.347%	$24.8555	$24.86	$24.85	$24.90
Purchase #5	$139.57	8.834%	$151.8996	$151.90	$151.90	$151.90
Purchase #6	$61.43	10.820%	$68.0767	$68.08	$68.10	$68.10
Purchase #7	$243.37	8.104%	$263.0927	$263.09	$263.10	$263.10
7 purchase totals =	$958.01		$1,025.8297	$1,025.84	$1,025.85	$1,025.90