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	$167.77	13.455%	$190.3435	$190.34	$190.35	$190.30
Purchase #2	$195.86	8.277%	$212.0713	$212.07	$212.05	$212.10
Purchase #3	$7.83	7.599%	$8.425	$8.43	$8.45	$8.40
Purchase #4	$98.74	4.751%	$103.4311	$103.43	$103.45	$103.40
Purchase #5	$199.90	10.307%	$220.5037	$220.50	$220.50	$220.50
Purchase #6	$248.83	3.492%	$257.5191	$257.52	$257.50	$257.50
Purchase #7	$9.82	6.160%	$10.4249	$10.42	$10.40	$10.40
7 purchase totals =	$928.75		$1,002.7186	$1,002.71	$1,002.70	$1,002.60