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	$189.84	12.658%	$213.8699	$213.87	$213.85	$213.90
Purchase #2	$116.65	3.656%	$120.9147	$120.91	$120.90	$120.90
Purchase #3	$212.42	11.361%	$236.553	$236.55	$236.55	$236.60
Purchase #4	$169.86	8.215%	$183.814	$183.81	$183.80	$183.80
Purchase #5	$82.51	10.869%	$91.478	$91.48	$91.50	$91.50
Purchase #6	$12.45	11.290%	$13.8556	$13.86	$13.85	$13.90
Purchase #7	$133.61	6.633%	$142.4724	$142.47	$142.45	$142.50
7 purchase totals =	$917.34		$1,002.9576	$1,002.95	$1,002.90	$1,003.10