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	$32.72	8.702%	$35.5673	$35.57	$35.55	$35.60
Purchase #2	$42.77	8.698%	$46.4901	$46.49	$46.50	$46.50
Purchase #3	$10.71	7.787%	$11.544	$11.54	$11.55	$11.50
Purchase #4	$40.93	5.576%	$43.2123	$43.21	$43.20	$43.20
Purchase #5	$166.49	5.578%	$175.7768	$175.78	$175.80	$175.80
Purchase #6	$239.90	11.829%	$268.2778	$268.28	$268.30	$268.30
Purchase #7	$170.60	5.447%	$179.8926	$179.89	$179.90	$179.90
7 purchase totals =	$704.12		$760.7609	$760.76	$760.80	$760.80