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	$220.75	3.154%	$227.7125	$227.71	$227.70	$227.70
Purchase #2	$200.94	7.477%	$215.9643	$215.96	$215.95	$216.00
Purchase #3	$147.67	3.281%	$152.5151	$152.52	$152.50	$152.50
Purchase #4	$36.30	8.777%	$39.4861	$39.49	$39.50	$39.50
Purchase #5	$176.56	4.467%	$184.4469	$184.45	$184.45	$184.40
Purchase #6	$52.29	7.134%	$56.0204	$56.02	$56.00	$56.00
Purchase #7	$205.59	4.653%	$215.1561	$215.16	$215.15	$215.20
7 purchase totals =	$1,040.10		$1,091.3014	$1,091.31	$1,091.25	$1,091.30