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	$224.37	11.644%	$250.4956	$250.50	$250.50	$250.50
Purchase #2	$13.73	7.520%	$14.7625	$14.76	$14.75	$14.80
Purchase #3	$55.57	6.231%	$59.0326	$59.03	$59.05	$59.00
Purchase #4	$42.96	5.492%	$45.3194	$45.32	$45.30	$45.30
Purchase #5	$235.69	9.197%	$257.3664	$257.37	$257.35	$257.40
Purchase #6	$109.94	3.202%	$113.4603	$113.46	$113.45	$113.50
Purchase #7	$222.90	8.584%	$242.0337	$242.03	$242.05	$242.00
7 purchase totals =	$905.16		$982.4705	$982.47	$982.45	$982.50