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	$29.76	10.160%	$32.7836	$32.78	$32.80	$32.80
Purchase #2	$38.60	11.127%	$42.895	$42.90	$42.90	$42.90
Purchase #3	$88.95	11.850%	$99.4906	$99.49	$99.50	$99.50
Purchase #4	$22.99	6.544%	$24.4945	$24.49	$24.50	$24.50
Purchase #5	$158.41	8.337%	$171.6166	$171.62	$171.60	$171.60
Purchase #6	$29.97	6.225%	$31.8356	$31.84	$31.85	$31.80
Purchase #7	$56.72	4.317%	$59.1686	$59.17	$59.15	$59.20
7 purchase totals =	$425.40		$462.2845	$462.29	$462.30	$462.30