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	$36.53	11.154%	$40.6046	$40.60	$40.60	$40.60
Purchase #2	$147.40	11.194%	$163.9	$163.90	$163.90	$163.90
Purchase #3	$54.38	9.495%	$59.5434	$59.54	$59.55	$59.50
Purchase #4	$20.40	11.769%	$22.8009	$22.80	$22.80	$22.80
Purchase #5	$82.88	13.834%	$94.3456	$94.35	$94.35	$94.30
Purchase #6	$234.55	3.491%	$242.7381	$242.74	$242.75	$242.70
Purchase #7	$78.66	5.799%	$83.2215	$83.22	$83.20	$83.20
7 purchase totals =	$654.80		$707.1541	$707.15	$707.15	$707.00