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	$119.68	3.293%	$123.6211	$123.62	$123.60	$123.60
Purchase #2	$86.88	4.162%	$90.4959	$90.50	$90.50	$90.50
Purchase #3	$94.58	12.703%	$106.5945	$106.59	$106.60	$106.60
Purchase #4	$239.33	6.658%	$255.2646	$255.26	$255.25	$255.30
Purchase #5	$119.30	12.475%	$134.1827	$134.18	$134.20	$134.20
Purchase #6	$39.95	3.372%	$41.2971	$41.30	$41.30	$41.30
Purchase #7	$120.27	4.578%	$125.776	$125.78	$125.80	$125.80
7 purchase totals =	$819.99		$877.2319	$877.23	$877.25	$877.30