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	$187.50	4.568%	$196.065	$196.07	$196.05	$196.10
Purchase #2	$250.63	11.665%	$279.866	$279.87	$279.85	$279.90
Purchase #3	$153.45	3.227%	$158.4018	$158.40	$158.40	$158.40
Purchase #4	$162.45	4.852%	$170.3321	$170.33	$170.35	$170.30
Purchase #5	$180.87	12.731%	$203.8966	$203.90	$203.90	$203.90
Purchase #6	$160.80	7.156%	$172.3068	$172.31	$172.30	$172.30
Purchase #7	$164.65	9.543%	$180.3625	$180.36	$180.35	$180.40
7 purchase totals =	$1,260.35		$1,361.2308	$1,361.24	$1,361.20	$1,361.30