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	$122.32	8.288%	$132.4579	$132.46	$132.45	$132.50
Purchase #2	$235.73	13.794%	$268.2466	$268.25	$268.25	$268.20
Purchase #3	$163.83	6.123%	$173.8613	$173.86	$173.85	$173.90
Purchase #4	$106.48	4.643%	$111.4239	$111.42	$111.40	$111.40
Purchase #5	$87.93	4.330%	$91.7374	$91.74	$91.75	$91.70
Purchase #6	$59.40	7.562%	$63.8918	$63.89	$63.90	$63.90
Purchase #7	$169.88	5.248%	$178.7953	$178.80	$178.80	$178.80
7 purchase totals =	$945.57		$1,020.4142	$1,020.42	$1,020.40	$1,020.40