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	$222.46	5.112%	$233.8322	$233.83	$233.85	$233.80
Purchase #2	$126.52	8.710%	$137.5399	$137.54	$137.55	$137.50
Purchase #3	$199.91	11.435%	$222.7697	$222.77	$222.75	$222.80
Purchase #4	$115.36	8.524%	$125.1933	$125.19	$125.20	$125.20
Purchase #5	$103.42	8.786%	$112.5065	$112.51	$112.50	$112.50
Purchase #6	$26.86	9.386%	$29.3811	$29.38	$29.40	$29.40
Purchase #7	$197.43	12.308%	$221.7297	$221.73	$221.75	$221.70
7 purchase totals =	$991.96		$1,082.9524	$1,082.95	$1,083.00	$1,082.90