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	$146.27	6.862%	$156.307	$156.31	$156.30	$156.30
Purchase #2	$29.91	9.780%	$32.8352	$32.84	$32.85	$32.80
Purchase #3	$218.36	11.135%	$242.6744	$242.67	$242.65	$242.70
Purchase #4	$77.55	5.225%	$81.602	$81.60	$81.60	$81.60
Purchase #5	$25.45	11.591%	$28.3999	$28.40	$28.40	$28.40
Purchase #6	$129.83	8.850%	$141.32	$141.32	$141.30	$141.30
Purchase #7	$111.47	11.142%	$123.89	$123.89	$123.90	$123.90
7 purchase totals =	$738.84		$807.0285	$807.03	$807.00	$807.00