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	$176.63	5.208%	$185.8289	$185.83	$185.85	$185.80
Purchase #2	$18.93	10.496%	$20.9169	$20.92	$20.90	$20.90
Purchase #3	$137.30	10.284%	$151.4199	$151.42	$151.40	$151.40
Purchase #4	$162.65	6.534%	$173.2776	$173.28	$173.30	$173.30
Purchase #5	$235.86	6.765%	$251.8159	$251.82	$251.80	$251.80
Purchase #6	$177.61	4.484%	$185.574	$185.57	$185.55	$185.60
Purchase #7	$69.75	3.193%	$71.9771	$71.98	$72.00	$72.00
7 purchase totals =	$978.73		$1,040.8103	$1,040.82	$1,040.80	$1,040.80