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	$133.77	5.208%	$140.7367	$140.74	$140.75	$140.70
Purchase #2	$25.86	5.633%	$27.3167	$27.32	$27.30	$27.30
Purchase #3	$187.89	5.650%	$198.5058	$198.51	$198.50	$198.50
Purchase #4	$92.62	11.789%	$103.539	$103.54	$103.55	$103.50
Purchase #5	$103.88	12.115%	$116.4651	$116.47	$116.45	$116.50
Purchase #6	$207.31	6.113%	$219.9829	$219.98	$220.00	$220.00
Purchase #7	$234.88	3.617%	$243.3756	$243.38	$243.40	$243.40
7 purchase totals =	$986.21		$1,049.9218	$1,049.94	$1,049.95	$1,049.90