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	$231.26	8.488%	$250.8893	$250.89	$250.90	$250.90
Purchase #2	$139.69	8.712%	$151.8598	$151.86	$151.85	$151.90
Purchase #3	$184.26	8.319%	$199.5886	$199.59	$199.60	$199.60
Purchase #4	$81.85	4.118%	$85.2206	$85.22	$85.20	$85.20
Purchase #5	$118.65	5.308%	$124.9479	$124.95	$124.95	$124.90
Purchase #6	$40.92	12.307%	$45.956	$45.96	$45.95	$46.00
Purchase #7	$83.70	6.392%	$89.0501	$89.05	$89.05	$89.10
7 purchase totals =	$880.33		$947.5123	$947.52	$947.50	$947.60