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	$103.62	6.652%	$110.5128	$110.51	$110.50	$110.50
Purchase #2	$70.46	3.392%	$72.85	$72.85	$72.85	$72.90
Purchase #3	$14.90	5.183%	$15.6723	$15.67	$15.65	$15.70
Purchase #4	$196.92	3.714%	$204.2336	$204.23	$204.25	$204.20
Purchase #5	$86.90	4.331%	$90.6636	$90.66	$90.65	$90.70
Purchase #6	$98.27	8.261%	$106.3881	$106.39	$106.40	$106.40
Purchase #7	$193.75	3.605%	$200.7347	$200.73	$200.75	$200.70
7 purchase totals =	$764.82		$801.0551	$801.04	$801.05	$801.10