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	$73.80	12.155%	$82.7704	$82.77	$82.75	$82.80
Purchase #2	$63.59	13.511%	$72.1816	$72.18	$72.20	$72.20
Purchase #3	$94.61	6.659%	$100.9101	$100.91	$100.90	$100.90
Purchase #4	$237.56	12.547%	$267.3667	$267.37	$267.35	$267.40
Purchase #5	$101.95	12.556%	$114.7508	$114.75	$114.75	$114.80
Purchase #6	$16.82	11.291%	$18.7191	$18.72	$18.70	$18.70
Purchase #7	$60.71	11.830%	$67.892	$67.89	$67.90	$67.90
7 purchase totals =	$649.04		$724.5907	$724.59	$724.55	$724.70