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	$136.47	4.299%	$142.3368	$142.34	$142.35	$142.30
Purchase #2	$64.74	4.681%	$67.7705	$67.77	$67.75	$67.80
Purchase #3	$142.64	9.389%	$156.0325	$156.03	$156.05	$156.00
Purchase #4	$226.70	6.248%	$240.8642	$240.86	$240.85	$240.90
Purchase #5	$204.65	12.591%	$230.4175	$230.42	$230.40	$230.40
Purchase #6	$33.76	13.542%	$38.3318	$38.33	$38.35	$38.30
Purchase #7	$173.54	13.363%	$196.7302	$196.73	$196.75	$196.70
7 purchase totals =	$982.50		$1,072.4835	$1,072.48	$1,072.50	$1,072.40