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	$199.68	12.848%	$225.3349	$225.33	$225.35	$225.30
Purchase #2	$97.98	5.582%	$103.4492	$103.45	$103.45	$103.40
Purchase #3	$180.73	13.797%	$205.6653	$205.67	$205.65	$205.70
Purchase #4	$155.71	6.263%	$165.4621	$165.46	$165.45	$165.50
Purchase #5	$70.73	10.380%	$78.0718	$78.07	$78.05	$78.10
Purchase #6	$37.90	5.236%	$39.8844	$39.88	$39.90	$39.90
Purchase #7	$160.36	5.277%	$168.8222	$168.82	$168.80	$168.80
7 purchase totals =	$903.09		$986.6899	$986.68	$986.65	$986.70