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	$158.85	8.302%	$172.0377	$172.04	$172.05	$172.00
Purchase #2	$52.95	7.839%	$57.1008	$57.10	$57.10	$57.10
Purchase #3	$238.56	7.264%	$255.889	$255.89	$255.90	$255.90
Purchase #4	$52.73	4.735%	$55.2268	$55.23	$55.25	$55.20
Purchase #5	$88.72	9.872%	$97.4784	$97.48	$97.50	$97.50
Purchase #6	$119.59	10.610%	$132.2785	$132.28	$132.30	$132.30
Purchase #7	$84.44	13.859%	$96.1425	$96.14	$96.15	$96.10
7 purchase totals =	$795.84		$866.1537	$866.16	$866.25	$866.10