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	$222.56	10.850%	$246.7078	$246.71	$246.70	$246.70
Purchase #2	$139.50	3.350%	$144.1733	$144.17	$144.15	$144.20
Purchase #3	$147.85	8.840%	$160.9199	$160.92	$160.90	$160.90
Purchase #4	$138.60	11.211%	$154.1384	$154.14	$154.15	$154.10
Purchase #5	$228.32	9.566%	$250.1611	$250.16	$250.15	$250.20
Purchase #6	$168.94	10.290%	$186.3239	$186.32	$186.30	$186.30
Purchase #7	$80.89	11.821%	$90.452	$90.45	$90.45	$90.50
7 purchase totals =	$1,126.66		$1,232.8764	$1,232.87	$1,232.80	$1,232.90