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	$184.57	10.278%	$203.5401	$203.54	$203.55	$203.50
Purchase #2	$176.51	4.530%	$184.5059	$184.51	$184.50	$184.50
Purchase #3	$35.34	6.184%	$37.5254	$37.53	$37.55	$37.50
Purchase #4	$86.86	4.568%	$90.8278	$90.83	$90.85	$90.80
Purchase #5	$189.68	8.425%	$205.6605	$205.66	$205.65	$205.70
Purchase #6	$173.76	10.630%	$192.2307	$192.23	$192.25	$192.20
Purchase #7	$16.33	6.117%	$17.3289	$17.33	$17.35	$17.30
7 purchase totals =	$863.05		$931.6193	$931.63	$931.70	$931.50