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	$118.34	3.732%	$122.7564	$122.76	$122.75	$122.80
Purchase #2	$142.33	9.163%	$155.3717	$155.37	$155.35	$155.40
Purchase #3	$12.76	4.240%	$13.301	$13.30	$13.30	$13.30
Purchase #4	$168.51	6.624%	$179.6721	$179.67	$179.65	$179.70
Purchase #5	$179.83	9.246%	$196.4571	$196.46	$196.45	$196.50
Purchase #6	$98.28	11.362%	$109.4466	$109.45	$109.45	$109.40
Purchase #7	$214.57	6.732%	$229.0149	$229.01	$229.00	$229.00
7 purchase totals =	$934.62		$1,006.0198	$1,006.02	$1,005.95	$1,006.10