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	$181.37	5.164%	$190.7359	$190.74	$190.75	$190.70
Purchase #2	$149.38	7.475%	$160.5462	$160.55	$160.55	$160.50
Purchase #3	$88.57	3.767%	$91.9064	$91.91	$91.90	$91.90
Purchase #4	$192.52	12.619%	$216.8141	$216.81	$216.80	$216.80
Purchase #5	$107.90	7.556%	$116.0529	$116.05	$116.05	$116.10
Purchase #6	$99.38	13.783%	$113.0775	$113.08	$113.10	$113.10
Purchase #7	$83.85	6.133%	$88.9925	$88.99	$89.00	$89.00
7 purchase totals =	$902.97		$978.1255	$978.13	$978.15	$978.10