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	$196.29	11.560%	$218.9811	$218.98	$219.00	$219.00
Purchase #2	$86.74	4.536%	$90.6745	$90.67	$90.65	$90.70
Purchase #3	$92.56	6.316%	$98.4061	$98.41	$98.40	$98.40
Purchase #4	$137.30	5.625%	$145.0231	$145.02	$145.00	$145.00
Purchase #5	$197.79	3.613%	$204.9362	$204.94	$204.95	$204.90
Purchase #6	$156.89	13.758%	$178.4749	$178.47	$178.45	$178.50
Purchase #7	$183.81	9.317%	$200.9356	$200.94	$200.95	$200.90
7 purchase totals =	$1,051.38		$1,137.4315	$1,137.43	$1,137.40	$1,137.40