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	$109.88	12.441%	$123.5502	$123.55	$123.55	$123.60
Purchase #2	$7.45	6.297%	$7.9191	$7.92	$7.90	$7.90
Purchase #3	$152.74	6.389%	$162.4986	$162.50	$162.50	$162.50
Purchase #4	$33.80	4.123%	$35.1936	$35.19	$35.20	$35.20
Purchase #5	$101.87	7.214%	$109.2189	$109.22	$109.20	$109.20
Purchase #6	$78.89	6.867%	$84.3074	$84.31	$84.30	$84.30
Purchase #7	$75.37	6.425%	$80.2125	$80.21	$80.20	$80.20
7 purchase totals =	$560.00		$602.9003	$602.90	$602.85	$602.90