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	$246.41	7.164%	$264.0628	$264.06	$264.05	$264.10
Purchase #2	$40.73	4.575%	$42.5934	$42.59	$42.60	$42.60
Purchase #3	$129.76	10.586%	$143.4964	$143.50	$143.50	$143.50
Purchase #4	$77.95	10.121%	$85.8393	$85.84	$85.85	$85.80
Purchase #5	$92.82	9.449%	$101.5906	$101.59	$101.60	$101.60
Purchase #6	$87.96	5.526%	$92.8207	$92.82	$92.80	$92.80
Purchase #7	$175.74	5.477%	$185.3653	$185.37	$185.35	$185.40
7 purchase totals =	$851.37		$915.7685	$915.77	$915.75	$915.80