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	$175.83	11.830%	$196.6307	$196.63	$196.65	$196.60
Purchase #2	$151.93	4.716%	$159.095	$159.10	$159.10	$159.10
Purchase #3	$115.77	7.508%	$124.462	$124.46	$124.45	$124.50
Purchase #4	$221.52	9.466%	$242.4891	$242.49	$242.50	$242.50
Purchase #5	$59.46	9.328%	$65.0064	$65.01	$65.00	$65.00
Purchase #6	$103.88	8.501%	$112.7108	$112.71	$112.70	$112.70
Purchase #7	$60.77	10.787%	$67.3253	$67.33	$67.35	$67.30
7 purchase totals =	$889.16		$967.7193	$967.73	$967.75	$967.70