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	$112.85	12.872%	$127.3761	$127.38	$127.40	$127.40
Purchase #2	$133.54	11.274%	$148.5953	$148.60	$148.60	$148.60
Purchase #3	$146.34	12.805%	$165.0788	$165.08	$165.10	$165.10
Purchase #4	$184.64	12.371%	$207.4818	$207.48	$207.50	$207.50
Purchase #5	$140.83	13.635%	$160.0322	$160.03	$160.05	$160.00
Purchase #6	$128.31	3.810%	$133.1986	$133.20	$133.20	$133.20
Purchase #7	$137.37	9.484%	$150.3982	$150.40	$150.40	$150.40
7 purchase totals =	$983.88		$1,092.1610	$1,092.17	$1,092.25	$1,092.20