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	$40.95	11.531%	$45.6719	$45.67	$45.65	$45.70
Purchase #2	$156.42	3.527%	$161.9369	$161.94	$161.95	$161.90
Purchase #3	$81.31	5.654%	$85.9073	$85.91	$85.90	$85.90
Purchase #4	$203.61	6.115%	$216.0608	$216.06	$216.05	$216.10
Purchase #5	$98.46	13.154%	$111.4114	$111.41	$111.40	$111.40
Purchase #6	$245.83	9.143%	$268.3062	$268.31	$268.30	$268.30
Purchase #7	$106.79	7.105%	$114.3774	$114.38	$114.40	$114.40
7 purchase totals =	$933.37		$1,003.6719	$1,003.68	$1,003.65	$1,003.70