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	$165.37	4.543%	$172.8828	$172.88	$172.90	$172.90
Purchase #2	$150.48	3.237%	$155.351	$155.35	$155.35	$155.40
Purchase #3	$123.54	3.296%	$127.6119	$127.61	$127.60	$127.60
Purchase #4	$197.96	8.111%	$214.0165	$214.02	$214.00	$214.00
Purchase #5	$230.35	4.582%	$240.9046	$240.90	$240.90	$240.90
Purchase #6	$245.72	7.189%	$263.3848	$263.38	$263.40	$263.40
Purchase #7	$206.80	5.646%	$218.4759	$218.48	$218.50	$218.50
7 purchase totals =	$1,320.22		$1,392.6275	$1,392.62	$1,392.65	$1,392.70