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	$96.60	3.403%	$99.8873	$99.89	$99.90	$99.90
Purchase #2	$209.61	8.812%	$228.0808	$228.08	$228.10	$228.10
Purchase #3	$181.69	6.526%	$193.5471	$193.55	$193.55	$193.50
Purchase #4	$38.48	13.236%	$43.5732	$43.57	$43.55	$43.60
Purchase #5	$131.89	6.441%	$140.385	$140.39	$140.40	$140.40
Purchase #6	$242.59	6.620%	$258.6495	$258.65	$258.65	$258.60
Purchase #7	$74.59	8.336%	$80.8078	$80.81	$80.80	$80.80
7 purchase totals =	$975.45		$1,044.9307	$1,044.94	$1,044.95	$1,044.90