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	$62.68	11.334%	$69.7842	$69.78	$69.80	$69.80
Purchase #2	$82.49	9.713%	$90.5023	$90.50	$90.50	$90.50
Purchase #3	$47.48	11.770%	$53.0684	$53.07	$53.05	$53.10
Purchase #4	$91.37	13.274%	$103.4985	$103.50	$103.50	$103.50
Purchase #5	$80.59	11.524%	$89.8772	$89.88	$89.90	$89.90
Purchase #6	$122.32	4.759%	$128.1412	$128.14	$128.15	$128.10
Purchase #7	$60.86	7.742%	$65.5718	$65.57	$65.55	$65.60
7 purchase totals =	$547.79		$600.4436	$600.44	$600.45	$600.50