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	$31.57	9.448%	$34.5527	$34.55	$34.55	$34.60
Purchase #2	$91.25	13.636%	$103.6929	$103.69	$103.70	$103.70
Purchase #3	$25.85	13.471%	$29.3323	$29.33	$29.35	$29.30
Purchase #4	$250.57	10.776%	$277.5714	$277.57	$277.55	$277.60
Purchase #5	$161.43	12.323%	$181.323	$181.32	$181.30	$181.30
Purchase #6	$81.35	11.695%	$90.8639	$90.86	$90.85	$90.90
Purchase #7	$212.87	10.212%	$234.6083	$234.61	$234.60	$234.60
7 purchase totals =	$854.89		$951.9445	$951.93	$951.90	$952.00