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	$46.80	3.515%	$48.445	$48.45	$48.45	$48.40
Purchase #2	$229.55	10.281%	$253.15	$253.15	$253.15	$253.20
Purchase #3	$115.90	6.633%	$123.5876	$123.59	$123.60	$123.60
Purchase #4	$41.29	5.353%	$43.5003	$43.50	$43.50	$43.50
Purchase #5	$147.43	11.578%	$164.4994	$164.50	$164.50	$164.50
Purchase #6	$235.26	10.358%	$259.6282	$259.63	$259.65	$259.60
Purchase #7	$75.35	13.751%	$85.7114	$85.71	$85.70	$85.70
7 purchase totals =	$891.58		$978.5219	$978.53	$978.55	$978.50