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	$91.45	7.536%	$98.3417	$98.34	$98.35	$98.30
Purchase #2	$185.91	4.145%	$193.616	$193.62	$193.60	$193.60
Purchase #3	$10.78	7.511%	$11.5897	$11.59	$11.60	$11.60
Purchase #4	$43.35	4.359%	$45.2396	$45.24	$45.25	$45.20
Purchase #5	$74.63	12.492%	$83.9528	$83.95	$83.95	$84.00
Purchase #6	$100.77	10.434%	$111.2843	$111.28	$111.30	$111.30
Purchase #7	$142.49	10.142%	$156.9413	$156.94	$156.95	$156.90
7 purchase totals =	$649.38		$700.9654	$700.96	$701.00	$700.90