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	$84.51	12.366%	$94.9605	$94.96	$94.95	$95.00
Purchase #2	$122.54	4.355%	$127.8766	$127.88	$127.90	$127.90
Purchase #3	$120.92	13.534%	$137.2853	$137.29	$137.30	$137.30
Purchase #4	$143.37	8.570%	$155.6568	$155.66	$155.65	$155.70
Purchase #5	$123.33	3.471%	$127.6108	$127.61	$127.60	$127.60
Purchase #6	$16.83	9.274%	$18.3908	$18.39	$18.40	$18.40
Purchase #7	$171.31	13.652%	$194.6972	$194.70	$194.70	$194.70
7 purchase totals =	$782.81		$856.4780	$856.49	$856.50	$856.60