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	$33.49	7.523%	$36.0095	$36.01	$36.00	$36.00
Purchase #2	$240.70	13.824%	$273.9744	$273.97	$273.95	$274.00
Purchase #3	$231.69	11.818%	$259.0711	$259.07	$259.05	$259.10
Purchase #4	$46.57	6.782%	$49.7284	$49.73	$49.75	$49.70
Purchase #5	$156.50	13.501%	$177.6291	$177.63	$177.65	$177.60
Purchase #6	$229.79	11.208%	$255.5449	$255.54	$255.55	$255.50
Purchase #7	$57.40	3.654%	$59.4974	$59.50	$59.50	$59.50
7 purchase totals =	$996.14		$1,111.4548	$1,111.45	$1,111.45	$1,111.40