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	$57.38	12.455%	$64.5267	$64.53	$64.55	$64.50
Purchase #2	$20.32	4.519%	$21.2383	$21.24	$21.25	$21.20
Purchase #3	$160.56	5.601%	$169.553	$169.55	$169.55	$169.60
Purchase #4	$129.54	8.114%	$140.0509	$140.05	$140.05	$140.10
Purchase #5	$102.54	6.376%	$109.078	$109.08	$109.10	$109.10
Purchase #6	$10.59	9.648%	$11.6117	$11.61	$11.60	$11.60
Purchase #7	$67.41	6.387%	$71.7155	$71.72	$71.70	$71.70
7 purchase totals =	$548.34		$587.7741	$587.78	$587.80	$587.80