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	$184.48	3.259%	$190.4922	$190.49	$190.50	$190.50
Purchase #2	$101.42	5.172%	$106.6654	$106.67	$106.65	$106.70
Purchase #3	$162.58	9.543%	$178.095	$178.10	$178.10	$178.10
Purchase #4	$109.42	13.544%	$124.2398	$124.24	$124.25	$124.20
Purchase #5	$176.55	13.504%	$200.3913	$200.39	$200.40	$200.40
Purchase #6	$107.77	3.795%	$111.8599	$111.86	$111.85	$111.90
Purchase #7	$6.65	13.668%	$7.5589	$7.56	$7.55	$7.60
7 purchase totals =	$848.87		$919.3025	$919.31	$919.30	$919.40