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	$34.68	8.640%	$37.6764	$37.68	$37.70	$37.70
Purchase #2	$238.90	7.527%	$256.882	$256.88	$256.90	$256.90
Purchase #3	$158.32	13.355%	$179.4636	$179.46	$179.45	$179.50
Purchase #4	$213.29	11.802%	$238.4625	$238.46	$238.45	$238.50
Purchase #5	$196.34	5.273%	$206.693	$206.69	$206.70	$206.70
Purchase #6	$200.66	7.294%	$215.2961	$215.30	$215.30	$215.30
Purchase #7	$57.78	13.812%	$65.7606	$65.76	$65.75	$65.80
7 purchase totals =	$1,099.97		$1,200.2342	$1,200.23	$1,200.25	$1,200.40