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	$123.44	11.151%	$137.2048	$137.20	$137.20	$137.20
Purchase #2	$142.78	11.117%	$158.6529	$158.65	$158.65	$158.70
Purchase #3	$149.89	10.683%	$165.9027	$165.90	$165.90	$165.90
Purchase #4	$37.60	5.318%	$39.5996	$39.60	$39.60	$39.60
Purchase #5	$6.81	11.128%	$7.5678	$7.57	$7.55	$7.60
Purchase #6	$98.95	9.191%	$108.0445	$108.04	$108.05	$108.00
Purchase #7	$99.81	6.500%	$106.2977	$106.30	$106.30	$106.30
7 purchase totals =	$659.28		$723.2700	$723.26	$723.25	$723.30