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	$228.75	12.527%	$257.4055	$257.41	$257.40	$257.40
Purchase #2	$5.98	7.521%	$6.4298	$6.43	$6.45	$6.40
Purchase #3	$120.57	9.305%	$131.789	$131.79	$131.80	$131.80
Purchase #4	$87.34	3.746%	$90.6118	$90.61	$90.60	$90.60
Purchase #5	$79.40	3.180%	$81.9249	$81.92	$81.90	$81.90
Purchase #6	$158.83	5.872%	$168.1565	$168.16	$168.15	$168.20
Purchase #7	$202.44	7.160%	$216.9347	$216.93	$216.95	$216.90
7 purchase totals =	$883.31		$953.2522	$953.25	$953.25	$953.20