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	$102.86	8.631%	$111.7378	$111.74	$111.75	$111.70
Purchase #2	$158.46	7.608%	$170.5156	$170.52	$170.50	$170.50
Purchase #3	$223.82	4.651%	$234.2299	$234.23	$234.25	$234.20
Purchase #4	$104.87	12.258%	$117.725	$117.73	$117.75	$117.70
Purchase #5	$126.83	7.796%	$136.7177	$136.72	$136.70	$136.70
Purchase #6	$191.48	4.729%	$200.5351	$200.54	$200.55	$200.50
Purchase #7	$44.48	8.779%	$48.3849	$48.38	$48.40	$48.40
7 purchase totals =	$952.80		$1,019.8460	$1,019.86	$1,019.90	$1,019.70