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	$175.97	12.687%	$198.2953	$198.30	$198.30	$198.30
Purchase #2	$114.59	7.618%	$123.3195	$123.32	$123.30	$123.30
Purchase #3	$166.44	7.138%	$178.3205	$178.32	$178.30	$178.30
Purchase #4	$240.99	6.290%	$256.1483	$256.15	$256.15	$256.10
Purchase #5	$25.88	6.297%	$27.5097	$27.51	$27.50	$27.50
Purchase #6	$49.67	9.163%	$54.2213	$54.22	$54.20	$54.20
Purchase #7	$232.29	12.575%	$261.5005	$261.50	$261.50	$261.50
7 purchase totals =	$1,005.83		$1,099.3151	$1,099.32	$1,099.25	$1,099.20