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	$52.46	13.859%	$59.7304	$59.73	$59.75	$59.70
Purchase #2	$139.94	11.339%	$155.8078	$155.81	$155.80	$155.80
Purchase #3	$92.72	13.231%	$104.9878	$104.99	$105.00	$105.00
Purchase #4	$132.31	3.861%	$137.4185	$137.42	$137.40	$137.40
Purchase #5	$106.67	7.645%	$114.8249	$114.82	$114.80	$114.80
Purchase #6	$239.76	11.152%	$266.498	$266.50	$266.50	$266.50
Purchase #7	$161.90	13.753%	$184.1661	$184.17	$184.15	$184.20
7 purchase totals =	$925.76		$1,023.4335	$1,023.44	$1,023.40	$1,023.40