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	$125.33	12.125%	$140.5263	$140.53	$140.55	$140.50
Purchase #2	$139.83	9.339%	$152.8887	$152.89	$152.90	$152.90
Purchase #3	$78.89	4.323%	$82.3004	$82.30	$82.30	$82.30
Purchase #4	$222.62	10.658%	$246.3468	$246.35	$246.35	$246.30
Purchase #5	$127.76	3.617%	$132.3811	$132.38	$132.40	$132.40
Purchase #6	$84.64	8.779%	$92.0705	$92.07	$92.05	$92.10
Purchase #7	$199.48	7.539%	$214.5188	$214.52	$214.50	$214.50
7 purchase totals =	$978.55		$1,061.0326	$1,061.04	$1,061.05	$1,061.00