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	$236.44	4.828%	$247.8553	$247.86	$247.85	$247.90
Purchase #2	$39.47	4.508%	$41.2493	$41.25	$41.25	$41.20
Purchase #3	$116.55	12.637%	$131.2784	$131.28	$131.30	$131.30
Purchase #4	$74.37	10.768%	$82.3782	$82.38	$82.40	$82.40
Purchase #5	$250.52	4.492%	$261.7734	$261.77	$261.75	$261.80
Purchase #6	$146.33	13.396%	$165.9324	$165.93	$165.95	$165.90
Purchase #7	$58.88	11.797%	$65.8261	$65.83	$65.85	$65.80
7 purchase totals =	$922.56		$996.2931	$996.30	$996.35	$996.30