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	$119.66	4.834%	$125.4444	$125.44	$125.45	$125.40
Purchase #2	$46.99	9.126%	$51.2783	$51.28	$51.30	$51.30
Purchase #3	$87.71	3.621%	$90.886	$90.89	$90.90	$90.90
Purchase #4	$80.41	7.650%	$86.5614	$86.56	$86.55	$86.60
Purchase #5	$221.83	10.394%	$244.887	$244.89	$244.90	$244.90
Purchase #6	$62.46	13.703%	$71.0189	$71.02	$71.00	$71.00
Purchase #7	$153.38	9.554%	$168.0339	$168.03	$168.05	$168.00
7 purchase totals =	$772.44		$838.1099	$838.11	$838.15	$838.10