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	$145.75	4.647%	$152.523	$152.52	$152.50	$152.50
Purchase #2	$26.99	10.752%	$29.892	$29.89	$29.90	$29.90
Purchase #3	$142.64	11.279%	$158.7284	$158.73	$158.75	$158.70
Purchase #4	$180.42	13.279%	$204.378	$204.38	$204.40	$204.40
Purchase #5	$58.81	4.167%	$61.2606	$61.26	$61.25	$61.30
Purchase #6	$100.78	11.497%	$112.3667	$112.37	$112.35	$112.40
Purchase #7	$50.42	6.790%	$53.8435	$53.84	$53.85	$53.80
7 purchase totals =	$705.81		$772.9922	$772.99	$773.00	$773.00