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	$159.95	4.398%	$166.9846	$166.98	$167.00	$167.00
Purchase #2	$182.78	6.204%	$194.1197	$194.12	$194.10	$194.10
Purchase #3	$117.98	12.638%	$132.8903	$132.89	$132.90	$132.90
Purchase #4	$219.83	8.147%	$237.7396	$237.74	$237.75	$237.70
Purchase #5	$171.43	6.443%	$182.4752	$182.48	$182.50	$182.50
Purchase #6	$189.62	3.649%	$196.5392	$196.54	$196.55	$196.50
Purchase #7	$240.26	10.498%	$265.4825	$265.48	$265.50	$265.50
7 purchase totals =	$1,281.85		$1,376.2311	$1,376.23	$1,376.30	$1,376.20