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	$158.72	4.770%	$166.2909	$166.29	$166.30	$166.30
Purchase #2	$222.29	4.289%	$231.824	$231.82	$231.80	$231.80
Purchase #3	$190.53	7.581%	$204.9741	$204.97	$204.95	$205.00
Purchase #4	$107.80	11.216%	$119.8908	$119.89	$119.90	$119.90
Purchase #5	$152.52	7.229%	$163.5457	$163.55	$163.55	$163.50
Purchase #6	$139.43	6.738%	$148.8248	$148.82	$148.80	$148.80
Purchase #7	$200.32	11.482%	$223.3207	$223.32	$223.30	$223.30
7 purchase totals =	$1,171.61		$1,258.6710	$1,258.66	$1,258.60	$1,258.60