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	$219.77	10.671%	$243.2217	$243.22	$243.20	$243.20
Purchase #2	$99.58	9.318%	$108.8589	$108.86	$108.85	$108.90
Purchase #3	$14.98	5.232%	$15.7638	$15.76	$15.75	$15.80
Purchase #4	$32.82	13.694%	$37.3144	$37.31	$37.30	$37.30
Purchase #5	$50.73	7.541%	$54.5555	$54.56	$54.55	$54.60
Purchase #6	$244.36	13.760%	$277.9839	$277.98	$278.00	$278.00
Purchase #7	$105.81	13.207%	$119.7843	$119.78	$119.80	$119.80
7 purchase totals =	$768.05		$857.4825	$857.47	$857.45	$857.60