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	$195.53	3.771%	$202.9034	$202.90	$202.90	$202.90
Purchase #2	$190.42	4.639%	$199.2536	$199.25	$199.25	$199.30
Purchase #3	$210.52	9.710%	$230.9615	$230.96	$230.95	$231.00
Purchase #4	$148.48	9.569%	$162.6881	$162.69	$162.70	$162.70
Purchase #5	$59.56	3.249%	$61.4951	$61.50	$61.50	$61.50
Purchase #6	$95.93	10.315%	$105.8252	$105.83	$105.85	$105.80
Purchase #7	$42.39	11.681%	$47.3416	$47.34	$47.35	$47.30
7 purchase totals =	$942.83		$1,010.4685	$1,010.47	$1,010.50	$1,010.50