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	$168.93	10.612%	$186.8569	$186.86	$186.85	$186.90
Purchase #2	$27.43	7.799%	$29.5693	$29.57	$29.55	$29.60
Purchase #3	$45.97	6.352%	$48.89	$48.89	$48.90	$48.90
Purchase #4	$83.57	6.503%	$89.0046	$89.00	$89.00	$89.00
Purchase #5	$25.55	13.414%	$28.9773	$28.98	$29.00	$29.00
Purchase #6	$218.95	4.818%	$229.499	$229.50	$229.50	$229.50
Purchase #7	$175.72	6.787%	$187.6461	$187.65	$187.65	$187.60
7 purchase totals =	$746.12		$800.4432	$800.45	$800.45	$800.50