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	$152.64	9.285%	$166.8126	$166.81	$166.80	$166.80
Purchase #2	$50.86	5.491%	$53.6527	$53.65	$53.65	$53.70
Purchase #3	$102.73	11.850%	$114.9035	$114.90	$114.90	$114.90
Purchase #4	$234.88	12.370%	$263.9347	$263.93	$263.95	$263.90
Purchase #5	$63.48	9.449%	$69.4782	$69.48	$69.50	$69.50
Purchase #6	$90.68	9.674%	$99.4524	$99.45	$99.45	$99.50
Purchase #7	$242.51	8.684%	$263.5696	$263.57	$263.55	$263.60
7 purchase totals =	$937.78		$1,031.8037	$1,031.79	$1,031.80	$1,031.90