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	$108.86	4.134%	$113.3603	$113.36	$113.35	$113.40
Purchase #2	$157.65	6.598%	$168.0517	$168.05	$168.05	$168.10
Purchase #3	$75.48	9.252%	$82.4634	$82.46	$82.45	$82.50
Purchase #4	$200.57	12.849%	$226.3412	$226.34	$226.35	$226.30
Purchase #5	$66.80	4.555%	$69.8427	$69.84	$69.85	$69.80
Purchase #6	$210.40	8.448%	$228.1746	$228.17	$228.15	$228.20
Purchase #7	$124.69	5.147%	$131.1078	$131.11	$131.10	$131.10
7 purchase totals =	$944.45		$1,019.3417	$1,019.33	$1,019.30	$1,019.40