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	$197.83	10.758%	$219.1126	$219.11	$219.10	$219.10
Purchase #2	$113.73	11.180%	$126.445	$126.45	$126.45	$126.40
Purchase #3	$198.25	9.659%	$217.399	$217.40	$217.40	$217.40
Purchase #4	$41.32	3.105%	$42.603	$42.60	$42.60	$42.60
Purchase #5	$30.56	7.209%	$32.7631	$32.76	$32.75	$32.80
Purchase #6	$40.34	3.140%	$41.6067	$41.61	$41.60	$41.60
Purchase #7	$55.93	5.839%	$59.1958	$59.20	$59.20	$59.20
7 purchase totals =	$677.96		$739.1252	$739.13	$739.10	$739.10