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	$221.43	4.483%	$231.3567	$231.36	$231.35	$231.40
Purchase #2	$181.88	12.333%	$204.3113	$204.31	$204.30	$204.30
Purchase #3	$72.59	13.311%	$82.2525	$82.25	$82.25	$82.30
Purchase #4	$238.55	7.257%	$255.8616	$255.86	$255.85	$255.90
Purchase #5	$111.54	10.766%	$123.5484	$123.55	$123.55	$123.50
Purchase #6	$62.52	13.514%	$70.969	$70.97	$70.95	$71.00
Purchase #7	$111.82	11.641%	$124.837	$124.84	$124.85	$124.80
7 purchase totals =	$1,000.33		$1,093.1365	$1,093.14	$1,093.10	$1,093.20