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	$132.32	13.368%	$150.0085	$150.01	$150.00	$150.00
Purchase #2	$40.38	5.561%	$42.6255	$42.63	$42.65	$42.60
Purchase #3	$173.35	3.154%	$178.8175	$178.82	$178.80	$178.80
Purchase #4	$184.66	5.538%	$194.8865	$194.89	$194.90	$194.90
Purchase #5	$101.57	9.266%	$110.9815	$110.98	$111.00	$111.00
Purchase #6	$167.75	9.758%	$184.119	$184.12	$184.10	$184.10
Purchase #7	$171.94	6.645%	$183.3654	$183.37	$183.35	$183.40
7 purchase totals =	$971.97		$1,044.8039	$1,044.82	$1,044.80	$1,044.80