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	$178.57	3.450%	$184.7307	$184.73	$184.75	$184.70
Purchase #2	$198.78	13.187%	$224.9931	$224.99	$225.00	$225.00
Purchase #3	$168.62	8.508%	$182.9662	$182.97	$182.95	$183.00
Purchase #4	$38.47	11.713%	$42.976	$42.98	$43.00	$43.00
Purchase #5	$178.56	10.253%	$196.8678	$196.87	$196.85	$196.90
Purchase #6	$48.68	11.730%	$54.3902	$54.39	$54.40	$54.40
Purchase #7	$178.64	7.188%	$191.4806	$191.48	$191.50	$191.50
7 purchase totals =	$990.32		$1,078.4046	$1,078.41	$1,078.45	$1,078.50