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	$99.83	12.698%	$112.5064	$112.51	$112.50	$112.50
Purchase #2	$196.93	11.218%	$219.0216	$219.02	$219.00	$219.00
Purchase #3	$114.76	7.433%	$123.2901	$123.29	$123.30	$123.30
Purchase #4	$195.46	6.816%	$208.7826	$208.78	$208.80	$208.80
Purchase #5	$196.71	4.335%	$205.2374	$205.24	$205.25	$205.20
Purchase #6	$9.74	11.531%	$10.8631	$10.86	$10.85	$10.90
Purchase #7	$47.52	4.234%	$49.532	$49.53	$49.55	$49.50
7 purchase totals =	$860.95		$929.2332	$929.23	$929.25	$929.20