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	$102.53	13.545%	$116.4177	$116.42	$116.40	$116.40
Purchase #2	$64.25	8.338%	$69.6072	$69.61	$69.60	$69.60
Purchase #3	$67.45	4.232%	$70.3045	$70.30	$70.30	$70.30
Purchase #4	$116.95	6.222%	$124.2266	$124.23	$124.25	$124.20
Purchase #5	$70.28	11.597%	$78.4304	$78.43	$78.45	$78.40
Purchase #6	$156.98	3.741%	$162.8526	$162.85	$162.85	$162.90
Purchase #7	$238.42	8.321%	$258.2589	$258.26	$258.25	$258.30
7 purchase totals =	$816.86		$880.0979	$880.10	$880.10	$880.10