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	$41.34	13.400%	$46.8796	$46.88	$46.90	$46.90
Purchase #2	$240.94	4.139%	$250.9125	$250.91	$250.90	$250.90
Purchase #3	$108.58	5.849%	$114.9308	$114.93	$114.95	$114.90
Purchase #4	$157.75	6.582%	$168.1331	$168.13	$168.15	$168.10
Purchase #5	$239.33	4.747%	$250.691	$250.69	$250.70	$250.70
Purchase #6	$91.96	8.772%	$100.0267	$100.03	$100.05	$100.00
Purchase #7	$73.99	6.511%	$78.8075	$78.81	$78.80	$78.80
7 purchase totals =	$953.89		$1,010.3812	$1,010.38	$1,010.45	$1,010.30