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	$35.97	3.566%	$37.2527	$37.25	$37.25	$37.30
Purchase #2	$183.71	13.366%	$208.2647	$208.26	$208.25	$208.30
Purchase #3	$110.43	3.137%	$113.8942	$113.89	$113.90	$113.90
Purchase #4	$192.50	4.344%	$200.8622	$200.86	$200.85	$200.90
Purchase #5	$29.46	9.718%	$32.3229	$32.32	$32.30	$32.30
Purchase #6	$196.37	4.269%	$204.753	$204.75	$204.75	$204.80
Purchase #7	$55.41	5.677%	$58.5556	$58.56	$58.55	$58.60
7 purchase totals =	$803.85		$855.9053	$855.89	$855.85	$856.10