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	$86.49	13.855%	$98.4732	$98.47	$98.45	$98.50
Purchase #2	$210.74	7.612%	$226.7815	$226.78	$226.80	$226.80
Purchase #3	$56.49	7.284%	$60.6047	$60.60	$60.60	$60.60
Purchase #4	$63.72	13.503%	$72.3241	$72.32	$72.30	$72.30
Purchase #5	$107.50	11.574%	$119.9421	$119.94	$119.95	$119.90
Purchase #6	$109.70	12.704%	$123.6363	$123.64	$123.65	$123.60
Purchase #7	$239.81	4.317%	$250.1626	$250.16	$250.15	$250.20
7 purchase totals =	$874.45		$951.9245	$951.91	$951.90	$951.90