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	$151.59	10.183%	$167.0264	$167.03	$167.05	$167.00
Purchase #2	$19.57	3.223%	$20.2007	$20.20	$20.20	$20.20
Purchase #3	$182.61	12.661%	$205.7303	$205.73	$205.75	$205.70
Purchase #4	$91.72	6.723%	$97.8863	$97.89	$97.90	$97.90
Purchase #5	$215.80	11.513%	$240.6451	$240.65	$240.65	$240.60
Purchase #6	$71.82	13.303%	$81.3742	$81.37	$81.35	$81.40
Purchase #7	$188.79	13.295%	$213.8896	$213.89	$213.90	$213.90
7 purchase totals =	$921.90		$1,026.7526	$1,026.76	$1,026.80	$1,026.70