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	$242.84	4.765%	$254.4113	$254.41	$254.40	$254.40
Purchase #2	$168.62	8.283%	$182.5868	$182.59	$182.60	$182.60
Purchase #3	$137.58	10.123%	$151.5072	$151.51	$151.50	$151.50
Purchase #4	$17.62	7.558%	$18.9517	$18.95	$18.95	$19.00
Purchase #5	$74.35	5.261%	$78.2616	$78.26	$78.25	$78.30
Purchase #6	$181.34	11.222%	$201.69	$201.69	$201.70	$201.70
Purchase #7	$37.56	8.849%	$40.8837	$40.88	$40.90	$40.90
7 purchase totals =	$859.91		$928.2923	$928.29	$928.30	$928.40