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	$145.40	3.526%	$150.5268	$150.53	$150.55	$150.50
Purchase #2	$180.46	13.234%	$204.3421	$204.34	$204.35	$204.30
Purchase #3	$133.35	13.400%	$151.2189	$151.22	$151.20	$151.20
Purchase #4	$238.85	10.457%	$263.8265	$263.83	$263.85	$263.80
Purchase #5	$125.81	8.153%	$136.0673	$136.07	$136.05	$136.10
Purchase #6	$59.49	4.311%	$62.0546	$62.05	$62.05	$62.10
Purchase #7	$93.67	10.147%	$103.1747	$103.17	$103.15	$103.20
7 purchase totals =	$977.03		$1,071.2109	$1,071.21	$1,071.20	$1,071.20