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	$232.44	4.188%	$242.1746	$242.17	$242.15	$242.20
Purchase #2	$72.66	6.720%	$77.5428	$77.54	$77.55	$77.50
Purchase #3	$200.27	6.337%	$212.9611	$212.96	$212.95	$213.00
Purchase #4	$65.47	8.696%	$71.1633	$71.16	$71.15	$71.20
Purchase #5	$180.36	6.367%	$191.8435	$191.84	$191.85	$191.80
Purchase #6	$214.39	11.834%	$239.7609	$239.76	$239.75	$239.80
Purchase #7	$102.70	8.438%	$111.3658	$111.37	$111.35	$111.40
7 purchase totals =	$1,068.29		$1,146.8120	$1,146.80	$1,146.75	$1,146.90