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	$127.89	3.298%	$132.1078	$132.11	$132.10	$132.10
Purchase #2	$61.34	9.826%	$67.3673	$67.37	$67.35	$67.40
Purchase #3	$185.38	5.826%	$196.1802	$196.18	$196.20	$196.20
Purchase #4	$136.64	5.386%	$143.9994	$144.00	$144.00	$144.00
Purchase #5	$160.72	9.833%	$176.5236	$176.52	$176.50	$176.50
Purchase #6	$191.40	5.589%	$202.0973	$202.10	$202.10	$202.10
Purchase #7	$116.78	9.633%	$128.0294	$128.03	$128.05	$128.00
7 purchase totals =	$980.15		$1,046.3050	$1,046.31	$1,046.30	$1,046.30