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	$73.36	10.805%	$81.2865	$81.29	$81.30	$81.30
Purchase #2	$216.72	10.484%	$239.4409	$239.44	$239.45	$239.40
Purchase #3	$77.80	6.644%	$82.969	$82.97	$82.95	$83.00
Purchase #4	$11.78	5.784%	$12.4614	$12.46	$12.45	$12.50
Purchase #5	$223.59	13.246%	$253.2067	$253.21	$253.20	$253.20
Purchase #6	$223.30	4.481%	$233.3061	$233.31	$233.30	$233.30
Purchase #7	$93.43	11.215%	$103.9082	$103.91	$103.90	$103.90
7 purchase totals =	$919.98		$1,006.5788	$1,006.59	$1,006.55	$1,006.60