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	$93.94	11.672%	$104.9047	$104.90	$104.90	$104.90
Purchase #2	$59.36	8.368%	$64.3272	$64.33	$64.35	$64.30
Purchase #3	$118.85	10.725%	$131.5967	$131.60	$131.60	$131.60
Purchase #4	$85.38	11.482%	$95.1833	$95.18	$95.20	$95.20
Purchase #5	$167.52	4.400%	$174.8909	$174.89	$174.90	$174.90
Purchase #6	$52.94	4.359%	$55.2477	$55.25	$55.25	$55.20
Purchase #7	$101.73	10.507%	$112.4188	$112.42	$112.40	$112.40
7 purchase totals =	$679.72		$738.5693	$738.57	$738.60	$738.50