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	$199.49	7.301%	$214.0548	$214.05	$214.05	$214.10
Purchase #2	$214.66	6.573%	$228.7696	$228.77	$228.75	$228.80
Purchase #3	$99.42	8.699%	$108.0685	$108.07	$108.05	$108.10
Purchase #4	$105.49	13.209%	$119.4242	$119.42	$119.40	$119.40
Purchase #5	$228.72	13.404%	$259.3776	$259.38	$259.40	$259.40
Purchase #6	$67.31	6.814%	$71.8965	$71.90	$71.90	$71.90
Purchase #7	$128.43	9.444%	$140.5589	$140.56	$140.55	$140.60
7 purchase totals =	$1,043.52		$1,142.1501	$1,142.15	$1,142.10	$1,142.30