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	$91.55	6.477%	$97.4797	$97.48	$97.50	$97.50
Purchase #2	$33.42	10.358%	$36.8816	$36.88	$36.90	$36.90
Purchase #3	$10.72	12.573%	$12.0678	$12.07	$12.05	$12.10
Purchase #4	$95.93	5.358%	$101.0699	$101.07	$101.05	$101.10
Purchase #5	$113.47	9.179%	$123.8854	$123.89	$123.90	$123.90
Purchase #6	$238.89	3.369%	$246.9382	$246.94	$246.95	$246.90
Purchase #7	$229.60	11.753%	$256.5849	$256.58	$256.60	$256.60
7 purchase totals =	$813.58		$874.9075	$874.91	$874.95	$875.00