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	$27.60	4.583%	$28.8649	$28.86	$28.85	$28.90
Purchase #2	$174.51	13.832%	$198.6482	$198.65	$198.65	$198.60
Purchase #3	$209.96	13.470%	$238.2416	$238.24	$238.25	$238.20
Purchase #4	$98.92	13.858%	$112.6283	$112.63	$112.65	$112.60
Purchase #5	$40.58	13.726%	$46.15	$46.15	$46.15	$46.20
Purchase #6	$7.85	12.719%	$8.8484	$8.85	$8.85	$8.80
Purchase #7	$49.47	7.414%	$53.1377	$53.14	$53.15	$53.10
7 purchase totals =	$608.89		$686.5191	$686.52	$686.55	$686.40