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	$63.66	10.375%	$70.2647	$70.26	$70.25	$70.30
Purchase #2	$234.61	10.424%	$259.0657	$259.07	$259.05	$259.10
Purchase #3	$150.68	13.867%	$171.5748	$171.57	$171.55	$171.60
Purchase #4	$111.61	7.442%	$119.916	$119.92	$119.90	$119.90
Purchase #5	$162.71	13.776%	$185.1249	$185.12	$185.10	$185.10
Purchase #6	$144.43	5.633%	$152.5657	$152.57	$152.55	$152.60
Purchase #7	$139.43	10.465%	$154.0213	$154.02	$154.00	$154.00
7 purchase totals =	$1,007.13		$1,112.5331	$1,112.53	$1,112.40	$1,112.60