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	$151.27	6.410%	$160.9664	$160.97	$160.95	$161.00
Purchase #2	$45.79	10.165%	$50.4446	$50.44	$50.45	$50.40
Purchase #3	$238.71	7.515%	$256.6491	$256.65	$256.65	$256.60
Purchase #4	$206.91	11.828%	$231.3833	$231.38	$231.40	$231.40
Purchase #5	$40.93	5.114%	$43.0232	$43.02	$43.00	$43.00
Purchase #6	$92.49	7.374%	$99.3102	$99.31	$99.30	$99.30
Purchase #7	$80.31	8.527%	$87.158	$87.16	$87.15	$87.20
7 purchase totals =	$856.41		$928.9348	$928.93	$928.90	$928.90