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	$168.52	13.735%	$191.6662	$191.67	$191.65	$191.70
Purchase #2	$100.83	4.475%	$105.3421	$105.34	$105.35	$105.30
Purchase #3	$149.44	7.394%	$160.4896	$160.49	$160.50	$160.50
Purchase #4	$215.81	8.104%	$233.2992	$233.30	$233.30	$233.30
Purchase #5	$97.77	6.439%	$104.0654	$104.07	$104.05	$104.10
Purchase #6	$208.90	9.689%	$229.1403	$229.14	$229.15	$229.10
Purchase #7	$126.47	12.140%	$141.8235	$141.82	$141.80	$141.80
7 purchase totals =	$1,067.74		$1,165.8263	$1,165.83	$1,165.80	$1,165.80