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	$56.98	8.171%	$61.6358	$61.64	$61.65	$61.60
Purchase #2	$131.81	7.780%	$142.0648	$142.06	$142.05	$142.10
Purchase #3	$155.31	9.659%	$170.3114	$170.31	$170.30	$170.30
Purchase #4	$177.95	9.676%	$195.1684	$195.17	$195.15	$195.20
Purchase #5	$147.98	5.628%	$156.3083	$156.31	$156.30	$156.30
Purchase #6	$85.50	11.703%	$95.5061	$95.51	$95.50	$95.50
Purchase #7	$48.74	4.296%	$50.8339	$50.83	$50.85	$50.80
7 purchase totals =	$804.27		$871.8287	$871.83	$871.80	$871.80