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	$41.53	11.778%	$46.4214	$46.42	$46.40	$46.40
Purchase #2	$23.44	9.259%	$25.6103	$25.61	$25.60	$25.60
Purchase #3	$68.97	3.689%	$71.5143	$71.51	$71.50	$71.50
Purchase #4	$74.40	10.245%	$82.0223	$82.02	$82.00	$82.00
Purchase #5	$184.50	11.516%	$205.747	$205.75	$205.75	$205.70
Purchase #6	$60.69	3.770%	$62.978	$62.98	$63.00	$63.00
Purchase #7	$109.29	13.582%	$124.1338	$124.13	$124.15	$124.10
7 purchase totals =	$562.82		$618.4271	$618.42	$618.40	$618.30