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	$183.93	3.811%	$190.9396	$190.94	$190.95	$190.90
Purchase #2	$77.88	5.699%	$82.3184	$82.32	$82.30	$82.30
Purchase #3	$75.36	4.645%	$78.8605	$78.86	$78.85	$78.90
Purchase #4	$133.36	10.713%	$147.6469	$147.65	$147.65	$147.60
Purchase #5	$246.81	8.630%	$268.1097	$268.11	$268.10	$268.10
Purchase #6	$23.60	7.611%	$25.3962	$25.40	$25.40	$25.40
Purchase #7	$134.34	13.419%	$152.3671	$152.37	$152.35	$152.40
7 purchase totals =	$875.28		$945.6384	$945.65	$945.60	$945.60