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	$127.47	12.787%	$143.7696	$143.77	$143.75	$143.80
Purchase #2	$120.88	9.302%	$132.1243	$132.12	$132.10	$132.10
Purchase #3	$215.56	3.320%	$222.7166	$222.72	$222.70	$222.70
Purchase #4	$103.33	9.325%	$112.9655	$112.97	$112.95	$113.00
Purchase #5	$146.33	4.108%	$152.3412	$152.34	$152.35	$152.30
Purchase #6	$175.85	9.607%	$192.7439	$192.74	$192.75	$192.70
Purchase #7	$38.58	7.505%	$41.4754	$41.48	$41.50	$41.50
7 purchase totals =	$928.00		$998.1365	$998.14	$998.10	$998.10