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	$161.83	4.451%	$169.0331	$169.03	$169.05	$169.00
Purchase #2	$86.89	13.207%	$98.3656	$98.37	$98.35	$98.40
Purchase #3	$60.93	9.839%	$66.9249	$66.92	$66.90	$66.90
Purchase #4	$231.60	3.722%	$240.2202	$240.22	$240.20	$240.20
Purchase #5	$75.64	3.854%	$78.5552	$78.56	$78.55	$78.60
Purchase #6	$9.47	9.104%	$10.3321	$10.33	$10.35	$10.30
Purchase #7	$235.40	12.627%	$265.124	$265.12	$265.10	$265.10
7 purchase totals =	$861.76		$928.5551	$928.55	$928.50	$928.50