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	$20.45	7.854%	$22.0561	$22.06	$22.05	$22.10
Purchase #2	$31.33	6.338%	$33.3157	$33.32	$33.30	$33.30
Purchase #3	$31.30	5.143%	$32.9098	$32.91	$32.90	$32.90
Purchase #4	$216.96	9.856%	$238.3436	$238.34	$238.35	$238.30
Purchase #5	$222.60	7.452%	$239.1882	$239.19	$239.20	$239.20
Purchase #6	$82.53	8.631%	$89.6532	$89.65	$89.65	$89.70
Purchase #7	$55.54	3.577%	$57.5267	$57.53	$57.55	$57.50
7 purchase totals =	$660.71		$712.9933	$713.00	$713.00	$713.00