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	$118.56	9.201%	$129.4687	$129.47	$129.45	$129.50
Purchase #2	$167.89	11.827%	$187.7464	$187.75	$187.75	$187.70
Purchase #3	$141.94	6.109%	$150.6111	$150.61	$150.60	$150.60
Purchase #4	$111.78	13.213%	$126.5495	$126.55	$126.55	$126.50
Purchase #5	$95.47	7.585%	$102.7114	$102.71	$102.70	$102.70
Purchase #6	$106.91	10.661%	$118.3077	$118.31	$118.30	$118.30
Purchase #7	$154.35	9.261%	$168.6444	$168.64	$168.65	$168.60
7 purchase totals =	$896.90		$984.0392	$984.04	$984.00	$983.90