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	$232.62	3.776%	$241.4037	$241.40	$241.40	$241.40
Purchase #2	$167.86	10.220%	$185.0153	$185.02	$185.00	$185.00
Purchase #3	$142.78	7.702%	$153.7769	$153.78	$153.80	$153.80
Purchase #4	$175.33	12.127%	$196.5923	$196.59	$196.60	$196.60
Purchase #5	$105.40	6.350%	$112.0929	$112.09	$112.10	$112.10
Purchase #6	$124.71	3.344%	$128.8803	$128.88	$128.90	$128.90
Purchase #7	$73.34	3.149%	$75.6495	$75.65	$75.65	$75.60
7 purchase totals =	$1,022.04		$1,093.4109	$1,093.41	$1,093.45	$1,093.40