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	$42.33	3.134%	$43.6566	$43.66	$43.65	$43.70
Purchase #2	$170.67	7.192%	$182.9446	$182.94	$182.95	$182.90
Purchase #3	$171.39	9.563%	$187.78	$187.78	$187.80	$187.80
Purchase #4	$56.53	5.302%	$59.5272	$59.53	$59.55	$59.50
Purchase #5	$205.39	5.182%	$216.0333	$216.03	$216.05	$216.00
Purchase #6	$174.78	13.439%	$198.2687	$198.27	$198.25	$198.30
Purchase #7	$200.92	10.789%	$222.5973	$222.60	$222.60	$222.60
7 purchase totals =	$1,022.01		$1,110.8077	$1,110.81	$1,110.85	$1,110.80