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	$113.94	4.456%	$119.0172	$119.02	$119.00	$119.00
Purchase #2	$166.28	7.178%	$178.2156	$178.22	$178.20	$178.20
Purchase #3	$141.74	10.330%	$156.3817	$156.38	$156.40	$156.40
Purchase #4	$69.87	11.780%	$78.1007	$78.10	$78.10	$78.10
Purchase #5	$60.44	10.174%	$66.5892	$66.59	$66.60	$66.60
Purchase #6	$118.97	6.560%	$126.7744	$126.77	$126.75	$126.80
Purchase #7	$137.53	11.170%	$152.8921	$152.89	$152.90	$152.90
7 purchase totals =	$808.77		$877.9709	$877.97	$877.95	$878.00