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	$68.25	6.799%	$72.8903	$72.89	$72.90	$72.90
Purchase #2	$229.66	7.668%	$247.2703	$247.27	$247.25	$247.30
Purchase #3	$22.81	9.784%	$25.0417	$25.04	$25.05	$25.00
Purchase #4	$111.37	9.435%	$121.8778	$121.88	$121.90	$121.90
Purchase #5	$178.55	12.282%	$200.4795	$200.48	$200.50	$200.50
Purchase #6	$148.36	6.729%	$158.3431	$158.34	$158.35	$158.30
Purchase #7	$205.77	13.465%	$233.4769	$233.48	$233.50	$233.50
7 purchase totals =	$964.77		$1,059.3796	$1,059.38	$1,059.45	$1,059.40