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	$231.46	9.445%	$253.3214	$253.32	$253.30	$253.30
Purchase #2	$152.37	13.415%	$172.8104	$172.81	$172.80	$172.80
Purchase #3	$55.40	6.542%	$59.0243	$59.02	$59.00	$59.00
Purchase #4	$9.76	7.546%	$10.4965	$10.50	$10.50	$10.50
Purchase #5	$54.66	4.475%	$57.106	$57.11	$57.10	$57.10
Purchase #6	$155.97	3.483%	$161.4024	$161.40	$161.40	$161.40
Purchase #7	$79.26	4.475%	$82.8069	$82.81	$82.80	$82.80
7 purchase totals =	$738.88		$796.9679	$796.97	$796.90	$796.90