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	$101.58	9.596%	$111.3276	$111.33	$111.35	$111.30
Purchase #2	$250.51	9.301%	$273.8099	$273.81	$273.80	$273.80
Purchase #3	$94.67	7.558%	$101.8252	$101.83	$101.85	$101.80
Purchase #4	$96.42	10.454%	$106.4997	$106.50	$106.50	$106.50
Purchase #5	$217.30	3.826%	$225.6139	$225.61	$225.60	$225.60
Purchase #6	$75.50	13.693%	$85.8382	$85.84	$85.85	$85.80
Purchase #7	$169.66	11.808%	$189.6935	$189.69	$189.70	$189.70
7 purchase totals =	$1,005.64		$1,094.6080	$1,094.61	$1,094.65	$1,094.50