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	$84.33	10.455%	$93.1467	$93.15	$93.15	$93.10
Purchase #2	$40.72	5.502%	$42.9604	$42.96	$42.95	$43.00
Purchase #3	$146.56	5.384%	$154.4508	$154.45	$154.45	$154.50
Purchase #4	$101.30	8.119%	$109.5245	$109.52	$109.50	$109.50
Purchase #5	$129.62	3.830%	$134.5844	$134.58	$134.60	$134.60
Purchase #6	$102.77	13.343%	$116.4826	$116.48	$116.50	$116.50
Purchase #7	$52.69	5.810%	$55.7513	$55.75	$55.75	$55.80
7 purchase totals =	$657.99		$706.9007	$706.89	$706.90	$707.00