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	$133.42	7.530%	$143.4665	$143.47	$143.45	$143.50
Purchase #2	$8.77	11.330%	$9.7636	$9.76	$9.75	$9.80
Purchase #3	$35.30	8.533%	$38.3121	$38.31	$38.30	$38.30
Purchase #4	$136.58	4.211%	$142.3314	$142.33	$142.35	$142.30
Purchase #5	$180.37	9.138%	$196.8522	$196.85	$196.85	$196.90
Purchase #6	$134.61	4.713%	$140.9542	$140.95	$140.95	$141.00
Purchase #7	$37.33	10.232%	$41.1496	$41.15	$41.15	$41.10
7 purchase totals =	$666.38		$712.8296	$712.82	$712.80	$712.90