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	$190.78	13.803%	$217.1134	$217.11	$217.10	$217.10
Purchase #2	$144.54	5.431%	$152.39	$152.39	$152.40	$152.40
Purchase #3	$127.96	13.330%	$145.0171	$145.02	$145.00	$145.00
Purchase #4	$67.80	8.823%	$73.782	$73.78	$73.80	$73.80
Purchase #5	$19.32	13.538%	$21.9355	$21.94	$21.95	$21.90
Purchase #6	$198.99	9.848%	$218.5865	$218.59	$218.60	$218.60
Purchase #7	$217.84	7.218%	$233.5637	$233.56	$233.55	$233.60
7 purchase totals =	$967.23		$1,062.3882	$1,062.39	$1,062.40	$1,062.40