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	$246.93	3.465%	$255.4861	$255.49	$255.50	$255.50
Purchase #2	$40.51	6.619%	$43.1914	$43.19	$43.20	$43.20
Purchase #3	$94.71	7.531%	$101.8426	$101.84	$101.85	$101.80
Purchase #4	$209.77	5.751%	$221.8339	$221.83	$221.85	$221.80
Purchase #5	$142.74	7.131%	$152.9188	$152.92	$152.90	$152.90
Purchase #6	$142.31	3.588%	$147.4161	$147.42	$147.40	$147.40
Purchase #7	$76.62	6.153%	$81.3344	$81.33	$81.35	$81.30
7 purchase totals =	$953.59		$1,004.0233	$1,004.02	$1,004.05	$1,003.90