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	$79.56	3.870%	$82.639	$82.64	$82.65	$82.60
Purchase #2	$130.31	13.742%	$148.2172	$148.22	$148.20	$148.20
Purchase #3	$72.47	12.654%	$81.6404	$81.64	$81.65	$81.60
Purchase #4	$110.85	4.785%	$116.1542	$116.15	$116.15	$116.20
Purchase #5	$67.78	11.504%	$75.5774	$75.58	$75.60	$75.60
Purchase #6	$89.44	7.679%	$96.3081	$96.31	$96.30	$96.30
Purchase #7	$121.59	8.790%	$132.2778	$132.28	$132.30	$132.30
7 purchase totals =	$672.00		$732.8141	$732.82	$732.85	$732.80