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	$91.66	3.244%	$94.6335	$94.63	$94.65	$94.60
Purchase #2	$203.60	7.306%	$218.475	$218.48	$218.50	$218.50
Purchase #3	$154.26	7.289%	$165.504	$165.50	$165.50	$165.50
Purchase #4	$34.34	4.404%	$35.8523	$35.85	$35.85	$35.90
Purchase #5	$92.77	8.782%	$100.9171	$100.92	$100.90	$100.90
Purchase #6	$187.65	4.482%	$196.0605	$196.06	$196.05	$196.10
Purchase #7	$60.72	10.229%	$66.931	$66.93	$66.95	$66.90
7 purchase totals =	$825.00		$878.3734	$878.37	$878.40	$878.40