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	$81.75	12.464%	$91.9393	$91.94	$91.95	$91.90
Purchase #2	$178.78	4.228%	$186.3388	$186.34	$186.35	$186.30
Purchase #3	$103.38	7.244%	$110.8688	$110.87	$110.85	$110.90
Purchase #4	$213.36	10.807%	$236.4178	$236.42	$236.40	$236.40
Purchase #5	$250.94	6.348%	$266.8697	$266.87	$266.85	$266.90
Purchase #6	$28.69	8.841%	$31.2265	$31.23	$31.25	$31.20
Purchase #7	$111.77	10.193%	$123.1627	$123.16	$123.15	$123.20
7 purchase totals =	$968.67		$1,046.8236	$1,046.83	$1,046.80	$1,046.80