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	$88.60	11.754%	$99.014	$99.01	$99.00	$99.00
Purchase #2	$5.41	3.864%	$5.619	$5.62	$5.60	$5.60
Purchase #3	$181.38	6.122%	$192.4841	$192.48	$192.50	$192.50
Purchase #4	$72.46	13.694%	$82.3827	$82.38	$82.40	$82.40
Purchase #5	$117.82	11.514%	$131.3858	$131.39	$131.40	$131.40
Purchase #6	$38.57	3.217%	$39.8108	$39.81	$39.80	$39.80
Purchase #7	$153.48	4.708%	$160.7058	$160.71	$160.70	$160.70
7 purchase totals =	$657.72		$711.4022	$711.40	$711.40	$711.40