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	$42.60	4.132%	$44.3602	$44.36	$44.35	$44.40
Purchase #2	$114.84	9.314%	$125.5362	$125.54	$125.55	$125.50
Purchase #3	$244.91	10.537%	$270.7162	$270.72	$270.70	$270.70
Purchase #4	$182.52	4.861%	$191.3923	$191.39	$191.40	$191.40
Purchase #5	$100.34	12.160%	$112.5413	$112.54	$112.55	$112.50
Purchase #6	$144.84	4.429%	$151.255	$151.26	$151.25	$151.30
Purchase #7	$179.66	8.236%	$194.4568	$194.46	$194.45	$194.50
7 purchase totals =	$1,009.71		$1,090.2580	$1,090.27	$1,090.25	$1,090.30