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	$82.95	13.643%	$94.2669	$94.27	$94.25	$94.30
Purchase #2	$150.46	5.283%	$158.4088	$158.41	$158.40	$158.40
Purchase #3	$61.43	11.140%	$68.2733	$68.27	$68.25	$68.30
Purchase #4	$158.39	3.681%	$164.2203	$164.22	$164.20	$164.20
Purchase #5	$74.89	3.334%	$77.3868	$77.39	$77.40	$77.40
Purchase #6	$104.89	8.253%	$113.5466	$113.55	$113.55	$113.50
Purchase #7	$129.72	10.815%	$143.7492	$143.75	$143.75	$143.70
7 purchase totals =	$762.73		$819.8519	$819.86	$819.80	$819.80