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	$179.82	11.751%	$200.9506	$200.95	$200.95	$201.00
Purchase #2	$89.50	6.257%	$95.1	$95.10	$95.10	$95.10
Purchase #3	$147.36	12.677%	$166.0408	$166.04	$166.05	$166.00
Purchase #4	$80.50	5.687%	$85.078	$85.08	$85.10	$85.10
Purchase #5	$173.93	9.437%	$190.3438	$190.34	$190.35	$190.30
Purchase #6	$75.82	3.144%	$78.2038	$78.20	$78.20	$78.20
Purchase #7	$59.63	8.675%	$64.8029	$64.80	$64.80	$64.80
7 purchase totals =	$806.56		$880.5199	$880.51	$880.55	$880.50