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	$155.50	7.325%	$166.8904	$166.89	$166.90	$166.90
Purchase #2	$18.51	5.605%	$19.5475	$19.55	$19.55	$19.50
Purchase #3	$92.72	6.477%	$98.7255	$98.73	$98.75	$98.70
Purchase #4	$173.30	4.145%	$180.4833	$180.48	$180.50	$180.50
Purchase #5	$165.82	9.316%	$181.2678	$181.27	$181.25	$181.30
Purchase #6	$35.38	9.737%	$38.825	$38.83	$38.85	$38.80
Purchase #7	$168.58	7.749%	$181.6433	$181.64	$181.65	$181.60
7 purchase totals =	$809.81		$867.3828	$867.39	$867.45	$867.30