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	$198.59	10.772%	$219.9821	$219.98	$220.00	$220.00
Purchase #2	$154.72	9.448%	$169.3379	$169.34	$169.35	$169.30
Purchase #3	$223.56	4.395%	$233.3855	$233.39	$233.40	$233.40
Purchase #4	$36.33	9.630%	$39.8286	$39.83	$39.85	$39.80
Purchase #5	$151.47	3.284%	$156.4443	$156.44	$156.45	$156.40
Purchase #6	$241.28	6.467%	$256.8836	$256.88	$256.90	$256.90
Purchase #7	$44.93	11.801%	$50.2322	$50.23	$50.25	$50.20
7 purchase totals =	$1,050.88		$1,126.0942	$1,126.09	$1,126.20	$1,126.00