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	$33.77	7.576%	$36.3284	$36.33	$36.35	$36.30
Purchase #2	$89.48	3.460%	$92.576	$92.58	$92.60	$92.60
Purchase #3	$78.31	4.869%	$82.1229	$82.12	$82.10	$82.10
Purchase #4	$63.33	5.153%	$66.5934	$66.59	$66.60	$66.60
Purchase #5	$9.30	13.741%	$10.5779	$10.58	$10.60	$10.60
Purchase #6	$99.79	3.128%	$102.9114	$102.91	$102.90	$102.90
Purchase #7	$39.87	11.496%	$44.4535	$44.45	$44.45	$44.50
7 purchase totals =	$413.85		$435.5635	$435.56	$435.60	$435.60