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	$174.79	4.614%	$182.8548	$182.85	$182.85	$182.90
Purchase #2	$69.78	3.217%	$72.0248	$72.02	$72.00	$72.00
Purchase #3	$93.50	13.600%	$106.216	$106.22	$106.20	$106.20
Purchase #4	$228.93	11.178%	$254.5198	$254.52	$254.50	$254.50
Purchase #5	$146.94	13.237%	$166.3904	$166.39	$166.40	$166.40
Purchase #6	$103.27	5.142%	$108.5801	$108.58	$108.60	$108.60
Purchase #7	$76.71	12.580%	$86.3601	$86.36	$86.35	$86.40
7 purchase totals =	$893.92		$976.9460	$976.94	$976.90	$977.00