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	$211.46	9.776%	$232.1323	$232.13	$232.15	$232.10
Purchase #2	$197.64	9.419%	$216.2557	$216.26	$216.25	$216.30
Purchase #3	$160.25	11.563%	$178.7797	$178.78	$178.80	$178.80
Purchase #4	$89.92	11.278%	$100.0612	$100.06	$100.05	$100.10
Purchase #5	$24.66	11.386%	$27.4678	$27.47	$27.45	$27.50
Purchase #6	$246.62	7.590%	$265.3385	$265.34	$265.35	$265.30
Purchase #7	$78.54	5.803%	$83.0977	$83.10	$83.10	$83.10
7 purchase totals =	$1,009.09		$1,103.1329	$1,103.14	$1,103.15	$1,103.20