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	$205.50	7.273%	$220.446	$220.45	$220.45	$220.40
Purchase #2	$144.81	10.212%	$159.598	$159.60	$159.60	$159.60
Purchase #3	$114.81	13.426%	$130.2244	$130.22	$130.20	$130.20
Purchase #4	$238.86	12.590%	$268.9325	$268.93	$268.95	$268.90
Purchase #5	$67.37	7.661%	$72.5312	$72.53	$72.55	$72.50
Purchase #6	$9.31	9.823%	$10.2245	$10.22	$10.20	$10.20
Purchase #7	$79.32	5.291%	$83.5168	$83.52	$83.50	$83.50
7 purchase totals =	$859.98		$945.4734	$945.47	$945.45	$945.30