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	$111.88	12.628%	$126.0082	$126.01	$126.00	$126.00
Purchase #2	$182.90	11.484%	$203.9042	$203.90	$203.90	$203.90
Purchase #3	$102.64	8.531%	$111.3962	$111.40	$111.40	$111.40
Purchase #4	$29.79	7.496%	$32.0231	$32.02	$32.00	$32.00
Purchase #5	$54.65	7.310%	$58.6449	$58.64	$58.65	$58.60
Purchase #6	$178.34	4.235%	$185.8927	$185.89	$185.90	$185.90
Purchase #7	$60.48	12.538%	$68.063	$68.06	$68.05	$68.10
7 purchase totals =	$720.68		$785.9323	$785.92	$785.90	$785.90