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	$99.33	9.826%	$109.0902	$109.09	$109.10	$109.10
Purchase #2	$143.76	4.868%	$150.7582	$150.76	$150.75	$150.80
Purchase #3	$15.46	13.630%	$17.5672	$17.57	$17.55	$17.60
Purchase #4	$232.79	12.812%	$262.6151	$262.62	$262.60	$262.60
Purchase #5	$40.77	11.594%	$45.4969	$45.50	$45.50	$45.50
Purchase #6	$157.40	13.315%	$178.3578	$178.36	$178.35	$178.40
Purchase #7	$231.89	8.194%	$250.8911	$250.89	$250.90	$250.90
7 purchase totals =	$921.40		$1,014.7765	$1,014.79	$1,014.75	$1,014.90