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	$175.94	3.525%	$182.1419	$182.14	$182.15	$182.10
Purchase #2	$89.66	10.391%	$98.9766	$98.98	$99.00	$99.00
Purchase #3	$242.98	7.788%	$261.9033	$261.90	$261.90	$261.90
Purchase #4	$167.77	7.588%	$180.5004	$180.50	$180.50	$180.50
Purchase #5	$134.80	11.597%	$150.4328	$150.43	$150.45	$150.40
Purchase #6	$88.39	11.805%	$98.8244	$98.82	$98.80	$98.80
Purchase #7	$191.79	10.857%	$212.6126	$212.61	$212.60	$212.60
7 purchase totals =	$1,091.33		$1,185.3920	$1,185.38	$1,185.40	$1,185.30