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	$206.78	3.824%	$214.6873	$214.69	$214.70	$214.70
Purchase #2	$73.34	6.424%	$78.0514	$78.05	$78.05	$78.10
Purchase #3	$78.27	11.852%	$87.5466	$87.55	$87.55	$87.50
Purchase #4	$134.92	12.698%	$152.0521	$152.05	$152.05	$152.10
Purchase #5	$86.82	9.695%	$95.2372	$95.24	$95.25	$95.20
Purchase #6	$245.95	13.401%	$278.9098	$278.91	$278.90	$278.90
Purchase #7	$35.90	13.333%	$40.6865	$40.69	$40.70	$40.70
7 purchase totals =	$861.98		$947.1709	$947.18	$947.20	$947.20