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	$151.71	7.186%	$162.6119	$162.61	$162.60	$162.60
Purchase #2	$116.69	13.145%	$132.0289	$132.03	$132.05	$132.00
Purchase #3	$134.36	5.616%	$141.9057	$141.91	$141.90	$141.90
Purchase #4	$79.74	11.844%	$89.1844	$89.18	$89.20	$89.20
Purchase #5	$116.80	5.805%	$123.5802	$123.58	$123.60	$123.60
Purchase #6	$166.28	3.264%	$171.7074	$171.71	$171.70	$171.70
Purchase #7	$30.94	3.468%	$32.013	$32.01	$32.00	$32.00
7 purchase totals =	$796.52		$853.0315	$853.03	$853.05	$853.00