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	$215.76	9.777%	$236.8549	$236.85	$236.85	$236.90
Purchase #2	$35.43	5.537%	$37.3918	$37.39	$37.40	$37.40
Purchase #3	$16.25	5.448%	$17.1353	$17.14	$17.15	$17.10
Purchase #4	$27.57	12.487%	$31.0127	$31.01	$31.00	$31.00
Purchase #5	$36.81	7.204%	$39.4618	$39.46	$39.45	$39.50
Purchase #6	$42.78	5.719%	$45.2266	$45.23	$45.25	$45.20
Purchase #7	$40.36	12.332%	$45.3372	$45.34	$45.35	$45.30
7 purchase totals =	$414.96		$452.4203	$452.42	$452.45	$452.40