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	$56.34	11.285%	$62.698	$62.70	$62.70	$62.70
Purchase #2	$233.32	4.774%	$244.4587	$244.46	$244.45	$244.50
Purchase #3	$90.47	12.621%	$101.8882	$101.89	$101.90	$101.90
Purchase #4	$85.78	6.751%	$91.571	$91.57	$91.55	$91.60
Purchase #5	$244.88	6.284%	$260.2683	$260.27	$260.25	$260.30
Purchase #6	$209.52	6.624%	$223.3986	$223.40	$223.40	$223.40
Purchase #7	$51.56	7.760%	$55.5611	$55.56	$55.55	$55.60
7 purchase totals =	$971.87		$1,039.8439	$1,039.85	$1,039.80	$1,040.00