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	$205.29	11.433%	$228.7608	$228.76	$228.75	$228.80
Purchase #2	$18.56	4.723%	$19.4366	$19.44	$19.45	$19.40
Purchase #3	$27.30	5.213%	$28.7231	$28.72	$28.70	$28.70
Purchase #4	$36.36	3.719%	$37.7122	$37.71	$37.70	$37.70
Purchase #5	$136.60	10.196%	$150.5277	$150.53	$150.55	$150.50
Purchase #6	$192.79	3.455%	$199.4509	$199.45	$199.45	$199.50
Purchase #7	$22.31	13.296%	$25.2763	$25.28	$25.30	$25.30
7 purchase totals =	$639.21		$689.8876	$689.89	$689.90	$689.90