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	$52.40	7.744%	$56.4579	$56.46	$56.45	$56.50
Purchase #2	$239.72	13.374%	$271.7802	$271.78	$271.80	$271.80
Purchase #3	$55.77	10.592%	$61.6772	$61.68	$61.70	$61.70
Purchase #4	$19.79	10.342%	$21.8367	$21.84	$21.85	$21.80
Purchase #5	$241.37	11.667%	$269.5306	$269.53	$269.55	$269.50
Purchase #6	$191.35	9.565%	$209.6526	$209.65	$209.65	$209.70
Purchase #7	$157.32	3.290%	$162.4958	$162.50	$162.50	$162.50
7 purchase totals =	$957.72		$1,053.4310	$1,053.44	$1,053.50	$1,053.50