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	$85.95	6.443%	$91.4878	$91.49	$91.50	$91.50
Purchase #2	$157.66	10.815%	$174.7109	$174.71	$174.70	$174.70
Purchase #3	$13.67	11.516%	$15.2442	$15.24	$15.25	$15.20
Purchase #4	$34.29	10.711%	$37.9628	$37.96	$37.95	$38.00
Purchase #5	$155.28	6.354%	$165.1465	$165.15	$165.15	$165.10
Purchase #6	$155.34	3.325%	$160.5051	$160.51	$160.50	$160.50
Purchase #7	$80.38	10.740%	$89.0128	$89.01	$89.00	$89.00
7 purchase totals =	$682.57		$734.0701	$734.07	$734.05	$734.00