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	$52.51	4.149%	$54.6886	$54.69	$54.70	$54.70
Purchase #2	$184.65	6.333%	$196.3439	$196.34	$196.35	$196.30
Purchase #3	$64.50	4.711%	$67.5386	$67.54	$67.55	$67.50
Purchase #4	$209.50	6.772%	$223.6873	$223.69	$223.70	$223.70
Purchase #5	$51.38	3.121%	$52.9836	$52.98	$53.00	$53.00
Purchase #6	$77.47	7.800%	$83.5127	$83.51	$83.50	$83.50
Purchase #7	$218.92	7.781%	$235.9542	$235.95	$235.95	$236.00
7 purchase totals =	$858.93		$914.7089	$914.70	$914.75	$914.70