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	$229.42	6.571%	$244.4952	$244.50	$244.50	$244.50
Purchase #2	$234.90	6.561%	$250.3118	$250.31	$250.30	$250.30
Purchase #3	$219.52	6.434%	$233.6439	$233.64	$233.65	$233.60
Purchase #4	$127.71	9.311%	$139.6011	$139.60	$139.60	$139.60
Purchase #5	$187.86	6.568%	$200.1986	$200.20	$200.20	$200.20
Purchase #6	$249.56	11.277%	$277.7029	$277.70	$277.70	$277.70
Purchase #7	$62.30	7.274%	$66.8317	$66.83	$66.85	$66.80
7 purchase totals =	$1,311.27		$1,412.7852	$1,412.78	$1,412.80	$1,412.70