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	$108.59	3.236%	$112.104	$112.10	$112.10	$112.10
Purchase #2	$7.57	11.137%	$8.4131	$8.41	$8.40	$8.40
Purchase #3	$30.48	3.127%	$31.4331	$31.43	$31.45	$31.40
Purchase #4	$16.55	9.463%	$18.1161	$18.12	$18.10	$18.10
Purchase #5	$58.62	7.263%	$62.8776	$62.88	$62.90	$62.90
Purchase #6	$85.64	5.596%	$90.4324	$90.43	$90.45	$90.40
Purchase #7	$52.97	8.763%	$57.6118	$57.61	$57.60	$57.60
7 purchase totals =	$360.42		$380.9881	$380.98	$381.00	$380.90