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	$108.39	13.869%	$123.4226	$123.42	$123.40	$123.40
Purchase #2	$89.82	11.267%	$99.94	$99.94	$99.95	$99.90
Purchase #3	$177.76	6.746%	$189.7517	$189.75	$189.75	$189.80
Purchase #4	$50.96	9.472%	$55.7869	$55.79	$55.80	$55.80
Purchase #5	$239.48	13.341%	$271.429	$271.43	$271.45	$271.40
Purchase #6	$164.46	11.507%	$183.3844	$183.38	$183.40	$183.40
Purchase #7	$225.25	10.400%	$248.676	$248.68	$248.70	$248.70
7 purchase totals =	$1,056.12		$1,172.3906	$1,172.39	$1,172.45	$1,172.40