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	$61.93	3.148%	$63.8796	$63.88	$63.90	$63.90
Purchase #2	$239.58	9.150%	$261.5016	$261.50	$261.50	$261.50
Purchase #3	$238.58	11.531%	$266.0907	$266.09	$266.10	$266.10
Purchase #4	$35.93	12.219%	$40.3203	$40.32	$40.30	$40.30
Purchase #5	$216.78	12.748%	$244.4151	$244.42	$244.40	$244.40
Purchase #6	$211.46	6.774%	$225.7843	$225.78	$225.80	$225.80
Purchase #7	$40.33	12.233%	$45.2636	$45.26	$45.25	$45.30
7 purchase totals =	$1,044.59		$1,147.2552	$1,147.25	$1,147.25	$1,147.30