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	$60.49	3.483%	$62.5969	$62.60	$62.60	$62.60
Purchase #2	$8.37	8.459%	$9.078	$9.08	$9.10	$9.10
Purchase #3	$199.38	11.488%	$222.2848	$222.28	$222.30	$222.30
Purchase #4	$194.48	5.646%	$205.4603	$205.46	$205.45	$205.50
Purchase #5	$175.61	13.591%	$199.4772	$199.48	$199.50	$199.50
Purchase #6	$131.70	4.260%	$137.3104	$137.31	$137.30	$137.30
Purchase #7	$142.35	11.275%	$158.4	$158.40	$158.40	$158.40
7 purchase totals =	$912.38		$994.6076	$994.61	$994.65	$994.70