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	$174.46	6.164%	$185.2137	$185.21	$185.20	$185.20
Purchase #2	$76.98	7.545%	$82.7881	$82.79	$82.80	$82.80
Purchase #3	$165.83	10.167%	$182.6899	$182.69	$182.70	$182.70
Purchase #4	$59.89	7.852%	$64.5926	$64.59	$64.60	$64.60
Purchase #5	$78.80	6.701%	$84.0804	$84.08	$84.10	$84.10
Purchase #6	$146.63	8.402%	$158.9499	$158.95	$158.95	$158.90
Purchase #7	$167.64	11.494%	$186.9085	$186.91	$186.90	$186.90
7 purchase totals =	$870.23		$945.2231	$945.22	$945.25	$945.20