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	$64.87	10.131%	$71.442	$71.44	$71.45	$71.40
Purchase #2	$51.79	5.846%	$54.8176	$54.82	$54.80	$54.80
Purchase #3	$164.72	13.832%	$187.5041	$187.50	$187.50	$187.50
Purchase #4	$40.79	8.799%	$44.3791	$44.38	$44.40	$44.40
Purchase #5	$162.83	13.322%	$184.5222	$184.52	$184.50	$184.50
Purchase #6	$80.60	5.501%	$85.0338	$85.03	$85.05	$85.00
Purchase #7	$219.30	3.691%	$227.3944	$227.39	$227.40	$227.40
7 purchase totals =	$784.90		$855.0932	$855.08	$855.10	$855.00