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	$197.87	12.288%	$222.1843	$222.18	$222.20	$222.20
Purchase #2	$247.57	3.469%	$256.1582	$256.16	$256.15	$256.20
Purchase #3	$7.52	4.481%	$7.857	$7.86	$7.85	$7.90
Purchase #4	$240.29	4.292%	$250.6032	$250.60	$250.60	$250.60
Purchase #5	$155.51	10.636%	$172.05	$172.05	$172.05	$172.10
Purchase #6	$30.26	9.732%	$33.2049	$33.20	$33.20	$33.20
Purchase #7	$84.90	11.332%	$94.5209	$94.52	$94.50	$94.50
7 purchase totals =	$963.92		$1,036.5785	$1,036.57	$1,036.55	$1,036.70