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	$215.79	7.109%	$231.1305	$231.13	$231.15	$231.10
Purchase #2	$125.35	9.750%	$137.5716	$137.57	$137.55	$137.60
Purchase #3	$73.41	12.614%	$82.6699	$82.67	$82.65	$82.70
Purchase #4	$240.87	7.873%	$259.8337	$259.83	$259.85	$259.80
Purchase #5	$79.41	12.805%	$89.5785	$89.58	$89.60	$89.60
Purchase #6	$244.39	13.480%	$277.3338	$277.33	$277.35	$277.30
Purchase #7	$200.25	4.272%	$208.8047	$208.80	$208.80	$208.80
7 purchase totals =	$1,179.47		$1,286.9227	$1,286.91	$1,286.95	$1,286.90