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	$156.72	5.297%	$165.0215	$165.02	$165.00	$165.00
Purchase #2	$26.49	12.325%	$29.7549	$29.75	$29.75	$29.80
Purchase #3	$159.47	5.858%	$168.8118	$168.81	$168.80	$168.80
Purchase #4	$151.49	4.633%	$158.5085	$158.51	$158.50	$158.50
Purchase #5	$77.61	6.455%	$82.6197	$82.62	$82.60	$82.60
Purchase #6	$31.32	6.503%	$33.3567	$33.36	$33.35	$33.40
Purchase #7	$212.50	4.861%	$222.8296	$222.83	$222.85	$222.80
7 purchase totals =	$815.60		$860.9027	$860.90	$860.85	$860.90