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	$153.59	8.803%	$167.1105	$167.11	$167.10	$167.10
Purchase #2	$134.76	6.454%	$143.4574	$143.46	$143.45	$143.50
Purchase #3	$228.91	11.269%	$254.7059	$254.71	$254.70	$254.70
Purchase #4	$162.53	10.344%	$179.3421	$179.34	$179.35	$179.30
Purchase #5	$164.96	10.686%	$182.5876	$182.59	$182.60	$182.60
Purchase #6	$87.81	4.853%	$92.0714	$92.07	$92.05	$92.10
Purchase #7	$91.88	5.451%	$96.8884	$96.89	$96.90	$96.90
7 purchase totals =	$1,024.44		$1,116.1633	$1,116.17	$1,116.15	$1,116.20