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	$118.62	12.521%	$133.4724	$133.47	$133.45	$133.50
Purchase #2	$199.90	7.737%	$215.3663	$215.37	$215.35	$215.40
Purchase #3	$171.74	4.824%	$180.0247	$180.02	$180.00	$180.00
Purchase #4	$156.36	12.705%	$176.2255	$176.23	$176.25	$176.20
Purchase #5	$57.72	5.412%	$60.8438	$60.84	$60.85	$60.80
Purchase #6	$139.49	13.330%	$158.084	$158.08	$158.10	$158.10
Purchase #7	$172.59	3.717%	$179.0052	$179.01	$179.00	$179.00
7 purchase totals =	$1,016.42		$1,103.0219	$1,103.02	$1,103.00	$1,103.00