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	$129.43	12.663%	$145.8197	$145.82	$145.80	$145.80
Purchase #2	$51.50	6.839%	$55.0221	$55.02	$55.00	$55.00
Purchase #3	$95.59	4.840%	$100.2166	$100.22	$100.20	$100.20
Purchase #4	$187.45	11.634%	$209.2579	$209.26	$209.25	$209.30
Purchase #5	$215.91	10.431%	$238.4316	$238.43	$238.45	$238.40
Purchase #6	$95.46	13.387%	$108.2392	$108.24	$108.25	$108.20
Purchase #7	$201.29	7.349%	$216.0828	$216.08	$216.10	$216.10
7 purchase totals =	$976.63		$1,073.0699	$1,073.07	$1,073.05	$1,073.00