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	$155.81	8.443%	$168.965	$168.97	$168.95	$169.00
Purchase #2	$165.43	8.772%	$179.9415	$179.94	$179.95	$179.90
Purchase #3	$157.73	13.712%	$179.3579	$179.36	$179.35	$179.40
Purchase #4	$64.53	10.152%	$71.0811	$71.08	$71.10	$71.10
Purchase #5	$20.94	3.356%	$21.6427	$21.64	$21.65	$21.60
Purchase #6	$63.96	11.865%	$71.5489	$71.55	$71.55	$71.50
Purchase #7	$172.38	11.508%	$192.2175	$192.22	$192.20	$192.20
7 purchase totals =	$800.78		$884.7546	$884.76	$884.75	$884.70