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	$78.71	9.862%	$86.4724	$86.47	$86.45	$86.50
Purchase #2	$20.94	6.401%	$22.2804	$22.28	$22.30	$22.30
Purchase #3	$240.96	5.551%	$254.3357	$254.34	$254.35	$254.30
Purchase #4	$48.67	8.504%	$52.8089	$52.81	$52.80	$52.80
Purchase #5	$24.94	11.639%	$27.8428	$27.84	$27.85	$27.80
Purchase #6	$202.39	10.607%	$223.8575	$223.86	$223.85	$223.90
Purchase #7	$72.89	10.580%	$80.6018	$80.60	$80.60	$80.60
7 purchase totals =	$689.50		$748.1995	$748.20	$748.20	$748.20