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	$174.96	12.442%	$196.7285	$196.73	$196.75	$196.70
Purchase #2	$215.90	6.353%	$229.6161	$229.62	$229.60	$229.60
Purchase #3	$187.53	11.659%	$209.3941	$209.39	$209.40	$209.40
Purchase #4	$125.28	4.122%	$130.444	$130.44	$130.45	$130.40
Purchase #5	$90.25	3.637%	$93.5324	$93.53	$93.55	$93.50
Purchase #6	$57.52	6.214%	$61.0943	$61.09	$61.10	$61.10
Purchase #7	$155.45	13.253%	$176.0518	$176.05	$176.05	$176.10
7 purchase totals =	$1,006.89		$1,096.8612	$1,096.85	$1,096.90	$1,096.80