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	$219.42	3.490%	$227.0778	$227.08	$227.10	$227.10
Purchase #2	$99.90	5.850%	$105.7442	$105.74	$105.75	$105.70
Purchase #3	$78.56	8.699%	$85.3939	$85.39	$85.40	$85.40
Purchase #4	$109.28	7.553%	$117.5339	$117.53	$117.55	$117.50
Purchase #5	$93.71	9.830%	$102.9217	$102.92	$102.90	$102.90
Purchase #6	$9.84	5.418%	$10.3731	$10.37	$10.35	$10.40
Purchase #7	$184.42	6.601%	$196.5936	$196.59	$196.60	$196.60
7 purchase totals =	$795.13		$845.6382	$845.62	$845.65	$845.60