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	$51.56	11.667%	$57.5755	$57.58	$57.60	$57.60
Purchase #2	$250.78	3.805%	$260.3222	$260.32	$260.30	$260.30
Purchase #3	$35.62	6.152%	$37.8113	$37.81	$37.80	$37.80
Purchase #4	$169.37	13.869%	$192.8599	$192.86	$192.85	$192.90
Purchase #5	$166.80	13.279%	$188.9494	$188.95	$188.95	$188.90
Purchase #6	$239.79	12.377%	$269.4688	$269.47	$269.45	$269.50
Purchase #7	$153.61	3.443%	$158.8988	$158.90	$158.90	$158.90
7 purchase totals =	$1,067.53		$1,165.8859	$1,165.89	$1,165.85	$1,165.90