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	$159.70	3.821%	$165.8021	$165.80	$165.80	$165.80
Purchase #2	$173.78	11.338%	$193.4832	$193.48	$193.50	$193.50
Purchase #3	$177.79	6.190%	$188.7952	$188.80	$188.80	$188.80
Purchase #4	$203.59	8.599%	$221.0967	$221.10	$221.10	$221.10
Purchase #5	$209.29	9.363%	$228.8858	$228.89	$228.90	$228.90
Purchase #6	$102.50	7.208%	$109.8882	$109.89	$109.90	$109.90
Purchase #7	$146.59	10.862%	$162.5126	$162.51	$162.50	$162.50
7 purchase totals =	$1,173.24		$1,270.4638	$1,270.47	$1,270.50	$1,270.50