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	$239.75	6.692%	$255.7941	$255.79	$255.80	$255.80
Purchase #2	$85.54	4.519%	$89.4056	$89.41	$89.40	$89.40
Purchase #3	$89.38	7.506%	$96.0889	$96.09	$96.10	$96.10
Purchase #4	$130.48	9.422%	$142.7738	$142.77	$142.75	$142.80
Purchase #5	$170.96	5.130%	$179.7302	$179.73	$179.75	$179.70
Purchase #6	$58.53	11.828%	$65.4529	$65.45	$65.45	$65.50
Purchase #7	$200.86	8.364%	$217.6599	$217.66	$217.65	$217.70
7 purchase totals =	$975.50		$1,046.9054	$1,046.90	$1,046.90	$1,047.00