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	$245.81	8.432%	$266.5367	$266.54	$266.55	$266.50
Purchase #2	$226.42	12.824%	$255.4561	$255.46	$255.45	$255.50
Purchase #3	$157.90	13.400%	$179.0586	$179.06	$179.05	$179.10
Purchase #4	$92.58	9.758%	$101.614	$101.61	$101.60	$101.60
Purchase #5	$55.30	4.286%	$57.6702	$57.67	$57.65	$57.70
Purchase #6	$84.85	6.742%	$90.5706	$90.57	$90.55	$90.60
Purchase #7	$70.73	6.700%	$75.4689	$75.47	$75.45	$75.50
7 purchase totals =	$933.59		$1,026.3751	$1,026.38	$1,026.30	$1,026.50