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	$105.31	4.307%	$109.8457	$109.85	$109.85	$109.80
Purchase #2	$140.28	10.818%	$155.4555	$155.46	$155.45	$155.50
Purchase #3	$220.49	10.365%	$243.3438	$243.34	$243.35	$243.30
Purchase #4	$51.38	11.430%	$57.2527	$57.25	$57.25	$57.30
Purchase #5	$68.46	5.752%	$72.3978	$72.40	$72.40	$72.40
Purchase #6	$133.52	3.814%	$138.6125	$138.61	$138.60	$138.60
Purchase #7	$181.39	4.595%	$189.7249	$189.72	$189.70	$189.70
7 purchase totals =	$900.83		$966.6329	$966.63	$966.60	$966.60