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	$58.91	11.250%	$65.5374	$65.54	$65.55	$65.50
Purchase #2	$33.86	5.143%	$35.6014	$35.60	$35.60	$35.60
Purchase #3	$250.53	4.659%	$262.2022	$262.20	$262.20	$262.20
Purchase #4	$29.64	6.370%	$31.5281	$31.53	$31.55	$31.50
Purchase #5	$137.28	3.542%	$142.1425	$142.14	$142.15	$142.10
Purchase #6	$177.37	10.831%	$196.5809	$196.58	$196.60	$196.60
Purchase #7	$43.29	4.700%	$45.3246	$45.32	$45.30	$45.30
7 purchase totals =	$730.88		$778.9171	$778.91	$778.95	$778.80