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	$174.51	5.479%	$184.0714	$184.07	$184.05	$184.10
Purchase #2	$175.96	13.220%	$199.2219	$199.22	$199.20	$199.20
Purchase #3	$196.51	10.686%	$217.5091	$217.51	$217.50	$217.50
Purchase #4	$225.32	13.278%	$255.238	$255.24	$255.25	$255.20
Purchase #5	$30.86	10.188%	$34.004	$34.00	$34.00	$34.00
Purchase #6	$11.78	6.148%	$12.5042	$12.50	$12.50	$12.50
Purchase #7	$62.76	12.119%	$70.3659	$70.37	$70.35	$70.40
7 purchase totals =	$877.70		$972.9145	$972.91	$972.85	$972.90