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	$97.74	8.387%	$105.9375	$105.94	$105.95	$105.90
Purchase #2	$147.61	8.776%	$160.5643	$160.56	$160.55	$160.60
Purchase #3	$96.48	8.158%	$104.3508	$104.35	$104.35	$104.40
Purchase #4	$157.89	6.732%	$168.5192	$168.52	$168.50	$168.50
Purchase #5	$215.34	9.192%	$235.1341	$235.13	$235.15	$235.10
Purchase #6	$152.57	10.698%	$168.8919	$168.89	$168.90	$168.90
Purchase #7	$58.65	12.108%	$65.7513	$65.75	$65.75	$65.80
7 purchase totals =	$926.28		$1,009.1491	$1,009.14	$1,009.15	$1,009.20