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	$63.92	13.216%	$72.3677	$72.37	$72.35	$72.40
Purchase #2	$113.59	8.308%	$123.0271	$123.03	$123.05	$123.00
Purchase #3	$150.64	11.173%	$167.471	$167.47	$167.45	$167.50
Purchase #4	$138.93	9.526%	$152.1645	$152.16	$152.15	$152.20
Purchase #5	$168.89	3.596%	$174.9633	$174.96	$174.95	$175.00
Purchase #6	$127.64	11.252%	$142.0021	$142.00	$142.00	$142.00
Purchase #7	$15.95	9.799%	$17.5129	$17.51	$17.50	$17.50
7 purchase totals =	$779.56		$849.5086	$849.50	$849.45	$849.60