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	$106.70	7.633%	$114.8444	$114.84	$114.85	$114.80
Purchase #2	$101.48	7.797%	$109.3924	$109.39	$109.40	$109.40
Purchase #3	$34.80	6.556%	$37.0815	$37.08	$37.10	$37.10
Purchase #4	$191.61	10.236%	$211.2232	$211.22	$211.20	$211.20
Purchase #5	$169.29	5.294%	$178.2522	$178.25	$178.25	$178.30
Purchase #6	$20.76	5.867%	$21.978	$21.98	$22.00	$22.00
Purchase #7	$131.39	12.294%	$147.5431	$147.54	$147.55	$147.50
7 purchase totals =	$756.03		$820.3148	$820.30	$820.35	$820.30