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	$60.58	9.472%	$66.3181	$66.32	$66.30	$66.30
Purchase #2	$25.32	7.733%	$27.278	$27.28	$27.30	$27.30
Purchase #3	$80.97	10.369%	$89.3658	$89.37	$89.35	$89.40
Purchase #4	$76.46	8.449%	$82.9201	$82.92	$82.90	$82.90
Purchase #5	$42.47	7.114%	$45.4913	$45.49	$45.50	$45.50
Purchase #6	$201.76	9.192%	$220.3058	$220.31	$220.30	$220.30
Purchase #7	$232.85	13.156%	$263.4837	$263.48	$263.50	$263.50
7 purchase totals =	$720.41		$795.1628	$795.17	$795.15	$795.20