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	$67.61	6.318%	$71.8816	$71.88	$71.90	$71.90
Purchase #2	$155.82	8.658%	$169.3109	$169.31	$169.30	$169.30
Purchase #3	$90.32	9.208%	$98.6367	$98.64	$98.65	$98.60
Purchase #4	$139.80	9.625%	$153.2558	$153.26	$153.25	$153.30
Purchase #5	$185.69	10.466%	$205.1243	$205.12	$205.10	$205.10
Purchase #6	$97.51	11.834%	$109.0493	$109.05	$109.05	$109.00
Purchase #7	$209.41	3.520%	$216.7812	$216.78	$216.80	$216.80
7 purchase totals =	$946.16		$1,024.0398	$1,024.04	$1,024.05	$1,024.00