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	$86.84	8.281%	$94.0312	$94.03	$94.05	$94.00
Purchase #2	$159.54	12.464%	$179.4251	$179.43	$179.45	$179.40
Purchase #3	$150.73	11.427%	$167.9539	$167.95	$167.95	$168.00
Purchase #4	$199.72	11.444%	$222.576	$222.58	$222.60	$222.60
Purchase #5	$56.52	9.429%	$61.8493	$61.85	$61.85	$61.80
Purchase #6	$71.33	7.102%	$76.3959	$76.40	$76.40	$76.40
Purchase #7	$210.94	12.309%	$236.9046	$236.90	$236.90	$236.90
7 purchase totals =	$935.62		$1,039.1360	$1,039.14	$1,039.20	$1,039.10