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	$178.77	6.400%	$190.2113	$190.21	$190.20	$190.20
Purchase #2	$34.50	7.184%	$36.9785	$36.98	$37.00	$37.00
Purchase #3	$116.69	9.257%	$127.492	$127.49	$127.50	$127.50
Purchase #4	$204.69	9.843%	$224.8376	$224.84	$224.85	$224.80
Purchase #5	$155.44	12.805%	$175.3441	$175.34	$175.35	$175.30
Purchase #6	$104.89	11.369%	$116.8149	$116.81	$116.80	$116.80
Purchase #7	$96.50	5.574%	$101.8789	$101.88	$101.90	$101.90
7 purchase totals =	$891.48		$973.5573	$973.55	$973.60	$973.50