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	$145.61	11.450%	$162.2823	$162.28	$162.30	$162.30
Purchase #2	$167.69	8.761%	$182.3813	$182.38	$182.40	$182.40
Purchase #3	$22.39	4.638%	$23.4284	$23.43	$23.45	$23.40
Purchase #4	$110.29	5.460%	$116.3118	$116.31	$116.30	$116.30
Purchase #5	$76.78	8.219%	$83.0905	$83.09	$83.10	$83.10
Purchase #6	$240.92	5.141%	$253.3057	$253.31	$253.30	$253.30
Purchase #7	$42.54	6.747%	$45.4102	$45.41	$45.40	$45.40
7 purchase totals =	$806.22		$866.2102	$866.21	$866.25	$866.20