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	$153.26	4.799%	$160.6149	$160.61	$160.60	$160.60
Purchase #2	$57.89	6.243%	$61.5041	$61.50	$61.50	$61.50
Purchase #3	$192.43	4.398%	$200.8931	$200.89	$200.90	$200.90
Purchase #4	$132.84	13.274%	$150.4732	$150.47	$150.45	$150.50
Purchase #5	$105.36	11.766%	$117.7567	$117.76	$117.75	$117.80
Purchase #6	$132.31	11.205%	$147.1353	$147.14	$147.15	$147.10
Purchase #7	$59.63	12.419%	$67.0354	$67.04	$67.05	$67.00
7 purchase totals =	$833.72		$905.4127	$905.41	$905.40	$905.40