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	$148.76	8.785%	$161.8286	$161.83	$161.85	$161.80
Purchase #2	$201.63	13.354%	$228.5557	$228.56	$228.55	$228.60
Purchase #3	$117.68	11.760%	$131.5192	$131.52	$131.50	$131.50
Purchase #4	$196.39	3.515%	$203.2931	$203.29	$203.30	$203.30
Purchase #5	$132.30	12.199%	$148.4393	$148.44	$148.45	$148.40
Purchase #6	$37.60	13.797%	$42.7877	$42.79	$42.80	$42.80
Purchase #7	$91.36	10.714%	$101.1483	$101.15	$101.15	$101.10
7 purchase totals =	$925.72		$1,017.5719	$1,017.58	$1,017.60	$1,017.50