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	$154.25	7.552%	$165.899	$165.90	$165.90	$165.90
Purchase #2	$133.94	6.637%	$142.8296	$142.83	$142.85	$142.80
Purchase #3	$197.97	10.347%	$218.454	$218.45	$218.45	$218.50
Purchase #4	$81.28	7.216%	$87.1452	$87.15	$87.15	$87.10
Purchase #5	$173.89	9.490%	$190.3922	$190.39	$190.40	$190.40
Purchase #6	$95.43	5.767%	$100.9334	$100.93	$100.95	$100.90
Purchase #7	$89.68	9.327%	$98.0445	$98.04	$98.05	$98.00
7 purchase totals =	$926.44		$1,003.6979	$1,003.69	$1,003.75	$1,003.60