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	$229.55	3.701%	$238.0456	$238.05	$238.05	$238.00
Purchase #2	$120.61	7.866%	$130.0972	$130.10	$130.10	$130.10
Purchase #3	$105.62	10.675%	$116.8949	$116.89	$116.90	$116.90
Purchase #4	$35.66	11.619%	$39.8033	$39.80	$39.80	$39.80
Purchase #5	$65.91	9.217%	$71.9849	$71.98	$72.00	$72.00
Purchase #6	$128.31	7.435%	$137.8498	$137.85	$137.85	$137.80
Purchase #7	$212.36	4.567%	$222.0585	$222.06	$222.05	$222.10
7 purchase totals =	$898.02		$956.7342	$956.73	$956.75	$956.70