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	$193.33	3.143%	$199.4064	$199.41	$199.40	$199.40
Purchase #2	$173.44	9.490%	$189.8995	$189.90	$189.90	$189.90
Purchase #3	$208.33	3.281%	$215.1653	$215.17	$215.15	$215.20
Purchase #4	$128.90	8.706%	$140.122	$140.12	$140.10	$140.10
Purchase #5	$222.83	7.199%	$238.8715	$238.87	$238.85	$238.90
Purchase #6	$225.88	5.146%	$237.5038	$237.50	$237.50	$237.50
Purchase #7	$139.88	11.160%	$155.4906	$155.49	$155.50	$155.50
7 purchase totals =	$1,292.59		$1,376.4591	$1,376.46	$1,376.40	$1,376.50