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	$119.75	3.404%	$123.8263	$123.83	$123.85	$123.80
Purchase #2	$161.87	11.720%	$180.8412	$180.84	$180.85	$180.80
Purchase #3	$75.75	9.697%	$83.0955	$83.10	$83.10	$83.10
Purchase #4	$55.85	11.867%	$62.4777	$62.48	$62.50	$62.50
Purchase #5	$207.71	6.654%	$221.531	$221.53	$221.55	$221.50
Purchase #6	$200.88	5.406%	$211.7396	$211.74	$211.75	$211.70
Purchase #7	$114.51	12.627%	$128.9692	$128.97	$128.95	$129.00
7 purchase totals =	$936.32		$1,012.4805	$1,012.49	$1,012.55	$1,012.40