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	$165.52	3.385%	$171.1229	$171.12	$171.10	$171.10
Purchase #2	$36.58	10.249%	$40.3291	$40.33	$40.35	$40.30
Purchase #3	$195.73	12.273%	$219.7519	$219.75	$219.75	$219.80
Purchase #4	$100.50	10.484%	$111.0364	$111.04	$111.05	$111.00
Purchase #5	$120.42	5.612%	$127.178	$127.18	$127.20	$127.20
Purchase #6	$80.26	8.366%	$86.9746	$86.97	$86.95	$87.00
Purchase #7	$242.31	11.854%	$271.0334	$271.03	$271.05	$271.00
7 purchase totals =	$941.32		$1,027.4263	$1,027.42	$1,027.45	$1,027.40