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	$171.77	4.584%	$179.6439	$179.64	$179.65	$179.60
Purchase #2	$188.92	4.214%	$196.8811	$196.88	$196.90	$196.90
Purchase #3	$197.54	3.438%	$204.3314	$204.33	$204.35	$204.30
Purchase #4	$75.56	10.609%	$83.5762	$83.58	$83.60	$83.60
Purchase #5	$174.98	12.723%	$197.2427	$197.24	$197.25	$197.20
Purchase #6	$91.33	11.196%	$101.5553	$101.56	$101.55	$101.60
Purchase #7	$181.39	6.322%	$192.8575	$192.86	$192.85	$192.90
7 purchase totals =	$1,081.49		$1,156.0881	$1,156.09	$1,156.15	$1,156.10