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	$70.93	10.238%	$78.1918	$78.19	$78.20	$78.20
Purchase #2	$164.69	3.145%	$169.8695	$169.87	$169.85	$169.90
Purchase #3	$203.40	10.716%	$225.1963	$225.20	$225.20	$225.20
Purchase #4	$11.98	11.679%	$13.3791	$13.38	$13.40	$13.40
Purchase #5	$118.66	10.616%	$131.2569	$131.26	$131.25	$131.30
Purchase #6	$218.93	12.772%	$246.8917	$246.89	$246.90	$246.90
Purchase #7	$194.91	7.316%	$209.1696	$209.17	$209.15	$209.20
7 purchase totals =	$983.50		$1,073.9549	$1,073.96	$1,073.95	$1,074.10