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	$93.25	11.162%	$103.6586	$103.66	$103.65	$103.70
Purchase #2	$218.74	7.362%	$234.8436	$234.84	$234.85	$234.80
Purchase #3	$71.89	7.861%	$77.5413	$77.54	$77.55	$77.50
Purchase #4	$225.25	4.468%	$235.3142	$235.31	$235.30	$235.30
Purchase #5	$78.34	5.320%	$82.5077	$82.51	$82.50	$82.50
Purchase #6	$138.33	9.662%	$151.6954	$151.70	$151.70	$151.70
Purchase #7	$72.44	11.666%	$80.8909	$80.89	$80.90	$80.90
7 purchase totals =	$898.24		$966.4517	$966.45	$966.45	$966.40