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	$172.49	13.512%	$195.7968	$195.80	$195.80	$195.80
Purchase #2	$71.61	7.682%	$77.1111	$77.11	$77.10	$77.10
Purchase #3	$87.48	6.154%	$92.8635	$92.86	$92.85	$92.90
Purchase #4	$237.59	7.262%	$254.8438	$254.84	$254.85	$254.80
Purchase #5	$101.89	6.452%	$108.4639	$108.46	$108.45	$108.50
Purchase #6	$86.72	13.762%	$98.6544	$98.65	$98.65	$98.70
Purchase #7	$243.50	5.332%	$256.4834	$256.48	$256.50	$256.50
7 purchase totals =	$1,001.28		$1,084.2169	$1,084.20	$1,084.20	$1,084.30