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	$123.84	8.703%	$134.6178	$134.62	$134.60	$134.60
Purchase #2	$204.49	9.309%	$223.526	$223.53	$223.55	$223.50
Purchase #3	$126.90	7.787%	$136.7817	$136.78	$136.80	$136.80
Purchase #4	$40.88	12.444%	$45.9671	$45.97	$45.95	$46.00
Purchase #5	$200.69	9.176%	$219.1053	$219.11	$219.10	$219.10
Purchase #6	$189.80	5.672%	$200.5655	$200.57	$200.55	$200.60
Purchase #7	$136.72	4.819%	$143.3085	$143.31	$143.30	$143.30
7 purchase totals =	$1,023.32		$1,103.8719	$1,103.89	$1,103.85	$1,103.90