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	$167.97	10.682%	$185.9126	$185.91	$185.90	$185.90
Purchase #2	$120.59	7.103%	$129.1555	$129.16	$129.15	$129.20
Purchase #3	$143.32	6.143%	$152.1241	$152.12	$152.10	$152.10
Purchase #4	$42.41	5.583%	$44.7778	$44.78	$44.80	$44.80
Purchase #5	$169.66	13.582%	$192.7032	$192.70	$192.70	$192.70
Purchase #6	$127.96	12.652%	$144.1495	$144.15	$144.15	$144.10
Purchase #7	$171.27	11.361%	$190.728	$190.73	$190.75	$190.70
7 purchase totals =	$943.18		$1,039.5507	$1,039.55	$1,039.55	$1,039.50