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	$62.29	6.210%	$66.1582	$66.16	$66.15	$66.20
Purchase #2	$31.80	3.542%	$32.9264	$32.93	$32.95	$32.90
Purchase #3	$168.56	9.434%	$184.462	$184.46	$184.45	$184.50
Purchase #4	$207.51	10.826%	$229.975	$229.98	$230.00	$230.00
Purchase #5	$250.56	10.332%	$276.4479	$276.45	$276.45	$276.40
Purchase #6	$57.26	9.780%	$62.86	$62.86	$62.85	$62.90
Purchase #7	$28.69	11.440%	$31.9721	$31.97	$31.95	$32.00
7 purchase totals =	$806.67		$884.8016	$884.81	$884.80	$884.90