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	$92.44	8.248%	$100.0645	$100.06	$100.05	$100.10
Purchase #2	$203.54	6.171%	$216.1005	$216.10	$216.10	$216.10
Purchase #3	$197.86	3.584%	$204.9513	$204.95	$204.95	$205.00
Purchase #4	$204.90	3.717%	$212.5161	$212.52	$212.50	$212.50
Purchase #5	$144.25	4.217%	$150.333	$150.33	$150.35	$150.30
Purchase #6	$34.25	8.589%	$37.1917	$37.19	$37.20	$37.20
Purchase #7	$100.83	13.152%	$114.0912	$114.09	$114.10	$114.10
7 purchase totals =	$978.07		$1,035.2483	$1,035.24	$1,035.25	$1,035.30