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	$130.52	11.831%	$145.9618	$145.96	$145.95	$146.00
Purchase #2	$126.95	5.766%	$134.2699	$134.27	$134.25	$134.30
Purchase #3	$125.38	9.529%	$137.3275	$137.33	$137.35	$137.30
Purchase #4	$241.64	11.754%	$270.0424	$270.04	$270.05	$270.00
Purchase #5	$108.57	7.659%	$116.8854	$116.89	$116.90	$116.90
Purchase #6	$178.93	3.778%	$185.69	$185.69	$185.70	$185.70
Purchase #7	$95.33	4.842%	$99.9459	$99.95	$99.95	$99.90
7 purchase totals =	$1,007.32		$1,090.1229	$1,090.13	$1,090.15	$1,090.10