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	$213.37	9.340%	$233.2988	$233.30	$233.30	$233.30
Purchase #2	$180.93	3.195%	$186.7107	$186.71	$186.70	$186.70
Purchase #3	$90.40	12.244%	$101.4686	$101.47	$101.45	$101.50
Purchase #4	$93.67	6.710%	$99.9553	$99.96	$99.95	$100.00
Purchase #5	$52.84	4.602%	$55.2717	$55.27	$55.25	$55.30
Purchase #6	$85.72	11.434%	$95.5212	$95.52	$95.50	$95.50
Purchase #7	$209.25	11.480%	$233.2719	$233.27	$233.25	$233.30
7 purchase totals =	$926.18		$1,005.4982	$1,005.50	$1,005.40	$1,005.60