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	$180.80	8.803%	$196.7158	$196.72	$196.70	$196.70
Purchase #2	$99.29	11.871%	$111.0767	$111.08	$111.10	$111.10
Purchase #3	$10.92	3.728%	$11.3271	$11.33	$11.35	$11.30
Purchase #4	$180.80	11.289%	$201.2105	$201.21	$201.20	$201.20
Purchase #5	$101.30	13.429%	$114.9036	$114.90	$114.90	$114.90
Purchase #6	$114.29	7.664%	$123.0492	$123.05	$123.05	$123.00
Purchase #7	$165.30	13.860%	$188.2106	$188.21	$188.20	$188.20
7 purchase totals =	$852.70		$946.4935	$946.50	$946.50	$946.40