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	$147.60	5.442%	$155.6324	$155.63	$155.65	$155.60
Purchase #2	$35.57	10.776%	$39.403	$39.40	$39.40	$39.40
Purchase #3	$174.32	11.525%	$194.4104	$194.41	$194.40	$194.40
Purchase #4	$235.29	4.376%	$245.5863	$245.59	$245.60	$245.60
Purchase #5	$218.59	3.661%	$226.5926	$226.59	$226.60	$226.60
Purchase #6	$78.59	3.500%	$81.3407	$81.34	$81.35	$81.30
Purchase #7	$55.91	12.591%	$62.9496	$62.95	$62.95	$62.90
7 purchase totals =	$945.87		$1,005.9150	$1,005.91	$1,005.95	$1,005.80