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	$55.43	3.756%	$57.512	$57.51	$57.50	$57.50
Purchase #2	$160.84	8.172%	$173.9838	$173.98	$174.00	$174.00
Purchase #3	$31.56	4.476%	$32.9726	$32.97	$32.95	$33.00
Purchase #4	$61.29	9.339%	$67.0139	$67.01	$67.00	$67.00
Purchase #5	$12.39	10.577%	$13.7005	$13.70	$13.70	$13.70
Purchase #6	$217.55	12.392%	$244.5088	$244.51	$244.50	$244.50
Purchase #7	$168.80	6.530%	$179.8226	$179.82	$179.80	$179.80
7 purchase totals =	$707.86		$769.5142	$769.50	$769.45	$769.50