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	$155.37	7.103%	$166.4059	$166.41	$166.40	$166.40
Purchase #2	$28.92	12.386%	$32.502	$32.50	$32.50	$32.50
Purchase #3	$134.69	9.838%	$147.9408	$147.94	$147.95	$147.90
Purchase #4	$87.54	3.235%	$90.3719	$90.37	$90.35	$90.40
Purchase #5	$97.70	9.404%	$106.8877	$106.89	$106.90	$106.90
Purchase #6	$160.36	7.561%	$172.4848	$172.48	$172.50	$172.50
Purchase #7	$224.52	6.215%	$238.4739	$238.47	$238.45	$238.50
7 purchase totals =	$889.10		$955.0670	$955.06	$955.05	$955.10