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	$73.67	11.352%	$82.033	$82.03	$82.05	$82.00
Purchase #2	$91.94	12.830%	$103.7359	$103.74	$103.75	$103.70
Purchase #3	$80.38	3.377%	$83.0944	$83.09	$83.10	$83.10
Purchase #4	$242.48	12.831%	$273.5926	$273.59	$273.60	$273.60
Purchase #5	$52.46	7.542%	$56.4165	$56.42	$56.40	$56.40
Purchase #6	$163.42	4.807%	$171.2756	$171.28	$171.30	$171.30
Purchase #7	$193.77	11.690%	$216.4217	$216.42	$216.40	$216.40
7 purchase totals =	$898.12		$986.5697	$986.57	$986.60	$986.50