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	$117.81	10.348%	$130.001	$130.00	$130.00	$130.00
Purchase #2	$7.32	13.665%	$8.3203	$8.32	$8.30	$8.30
Purchase #3	$179.74	5.711%	$190.005	$190.01	$190.00	$190.00
Purchase #4	$164.89	12.229%	$185.0544	$185.05	$185.05	$185.10
Purchase #5	$46.85	10.193%	$51.6254	$51.63	$51.65	$51.60
Purchase #6	$88.40	12.353%	$99.3201	$99.32	$99.30	$99.30
Purchase #7	$181.63	7.796%	$195.7899	$195.79	$195.80	$195.80
7 purchase totals =	$786.64		$860.1161	$860.12	$860.10	$860.10