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	$167.84	10.536%	$185.5236	$185.52	$185.50	$185.50
Purchase #2	$219.96	8.394%	$238.4234	$238.42	$238.40	$238.40
Purchase #3	$186.91	4.599%	$195.506	$195.51	$195.50	$195.50
Purchase #4	$218.47	4.636%	$228.5983	$228.60	$228.60	$228.60
Purchase #5	$221.85	7.500%	$238.4888	$238.49	$238.50	$238.50
Purchase #6	$44.74	3.626%	$46.3623	$46.36	$46.35	$46.40
Purchase #7	$30.48	7.481%	$32.7602	$32.76	$32.75	$32.80
7 purchase totals =	$1,090.25		$1,165.6626	$1,165.66	$1,165.60	$1,165.70