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	$174.93	12.187%	$196.2487	$196.25	$196.25	$196.20
Purchase #2	$101.37	9.122%	$110.617	$110.62	$110.60	$110.60
Purchase #3	$162.27	7.160%	$173.8885	$173.89	$173.90	$173.90
Purchase #4	$116.42	13.319%	$131.926	$131.93	$131.95	$131.90
Purchase #5	$26.32	3.105%	$27.1372	$27.14	$27.15	$27.10
Purchase #6	$106.78	12.565%	$120.1969	$120.20	$120.20	$120.20
Purchase #7	$139.88	4.601%	$146.3159	$146.32	$146.30	$146.30
7 purchase totals =	$827.97		$906.3302	$906.35	$906.35	$906.20