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	$166.73	4.714%	$174.5897	$174.59	$174.60	$174.60
Purchase #2	$146.39	6.386%	$155.7385	$155.74	$155.75	$155.70
Purchase #3	$169.50	6.654%	$180.7785	$180.78	$180.80	$180.80
Purchase #4	$199.55	4.574%	$208.6774	$208.68	$208.70	$208.70
Purchase #5	$36.72	10.302%	$40.5029	$40.50	$40.50	$40.50
Purchase #6	$168.37	13.689%	$191.4182	$191.42	$191.40	$191.40
Purchase #7	$91.26	10.268%	$100.6306	$100.63	$100.65	$100.60
7 purchase totals =	$978.52		$1,052.3358	$1,052.34	$1,052.40	$1,052.30