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	$178.72	5.657%	$188.8302	$188.83	$188.85	$188.80
Purchase #2	$80.29	5.551%	$84.7469	$84.75	$84.75	$84.70
Purchase #3	$150.37	12.457%	$169.1016	$169.10	$169.10	$169.10
Purchase #4	$106.35	4.679%	$111.3261	$111.33	$111.35	$111.30
Purchase #5	$185.51	13.516%	$210.5835	$210.58	$210.60	$210.60
Purchase #6	$237.82	13.216%	$269.2503	$269.25	$269.25	$269.30
Purchase #7	$114.42	6.215%	$121.5312	$121.53	$121.55	$121.50
7 purchase totals =	$1,053.48		$1,155.3698	$1,155.37	$1,155.45	$1,155.30