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	$135.89	11.870%	$152.0201	$152.02	$152.00	$152.00
Purchase #2	$25.53	13.151%	$28.8875	$28.89	$28.90	$28.90
Purchase #3	$155.79	12.215%	$174.8197	$174.82	$174.80	$174.80
Purchase #4	$126.25	12.570%	$142.1196	$142.12	$142.10	$142.10
Purchase #5	$239.55	9.604%	$262.5564	$262.56	$262.55	$262.60
Purchase #6	$27.67	4.136%	$28.8144	$28.81	$28.80	$28.80
Purchase #7	$212.89	11.725%	$237.8514	$237.85	$237.85	$237.90
7 purchase totals =	$923.57		$1,027.0691	$1,027.07	$1,027.00	$1,027.10