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	$196.31	13.476%	$222.7647	$222.76	$222.75	$222.80
Purchase #2	$166.68	10.458%	$184.1114	$184.11	$184.10	$184.10
Purchase #3	$81.61	10.189%	$89.9252	$89.93	$89.95	$89.90
Purchase #4	$197.64	8.259%	$213.9631	$213.96	$213.95	$214.00
Purchase #5	$52.43	3.220%	$54.1182	$54.12	$54.10	$54.10
Purchase #6	$58.40	12.636%	$65.7794	$65.78	$65.80	$65.80
Purchase #7	$86.89	9.710%	$95.327	$95.33	$95.35	$95.30
7 purchase totals =	$839.96		$925.9890	$925.99	$926.00	$926.00