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	$113.40	12.531%	$127.6102	$127.61	$127.60	$127.60
Purchase #2	$110.62	13.511%	$125.5659	$125.57	$125.55	$125.60
Purchase #3	$149.96	8.191%	$162.2432	$162.24	$162.25	$162.20
Purchase #4	$56.89	4.451%	$59.4222	$59.42	$59.40	$59.40
Purchase #5	$112.82	12.398%	$126.8074	$126.81	$126.80	$126.80
Purchase #6	$55.26	11.850%	$61.8083	$61.81	$61.80	$61.80
Purchase #7	$129.67	8.104%	$140.1785	$140.18	$140.20	$140.20
7 purchase totals =	$728.62		$803.6357	$803.64	$803.60	$803.60