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	$197.89	3.236%	$204.2937	$204.29	$204.30	$204.30
Purchase #2	$102.73	11.302%	$114.3405	$114.34	$114.35	$114.30
Purchase #3	$44.59	9.661%	$48.8978	$48.90	$48.90	$48.90
Purchase #4	$236.61	4.220%	$246.5949	$246.59	$246.60	$246.60
Purchase #5	$203.73	6.205%	$216.3714	$216.37	$216.35	$216.40
Purchase #6	$98.92	3.766%	$102.6453	$102.65	$102.65	$102.60
Purchase #7	$100.65	10.798%	$111.5182	$111.52	$111.50	$111.50
7 purchase totals =	$985.12		$1,044.6618	$1,044.66	$1,044.65	$1,044.60