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	$86.51	9.114%	$94.3945	$94.39	$94.40	$94.40
Purchase #2	$96.31	13.746%	$109.5488	$109.55	$109.55	$109.50
Purchase #3	$126.93	10.732%	$140.5521	$140.55	$140.55	$140.60
Purchase #4	$129.75	6.167%	$137.7517	$137.75	$137.75	$137.80
Purchase #5	$70.48	3.435%	$72.901	$72.90	$72.90	$72.90
Purchase #6	$19.39	13.229%	$21.9551	$21.96	$21.95	$22.00
Purchase #7	$78.59	8.355%	$85.1562	$85.16	$85.15	$85.20
7 purchase totals =	$607.96		$662.2594	$662.26	$662.25	$662.40