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	$40.85	11.126%	$45.395	$45.40	$45.40	$45.40
Purchase #2	$151.25	3.648%	$156.7676	$156.77	$156.75	$156.80
Purchase #3	$113.51	6.277%	$120.635	$120.64	$120.65	$120.60
Purchase #4	$145.53	3.345%	$150.398	$150.40	$150.40	$150.40
Purchase #5	$109.36	8.496%	$118.6512	$118.65	$118.65	$118.70
Purchase #6	$95.37	10.681%	$105.5565	$105.56	$105.55	$105.60
Purchase #7	$91.45	3.457%	$94.6114	$94.61	$94.60	$94.60
7 purchase totals =	$747.32		$792.0147	$792.03	$792.00	$792.10