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	$78.39	13.566%	$89.0244	$89.02	$89.00	$89.00
Purchase #2	$234.54	10.225%	$258.5217	$258.52	$258.50	$258.50
Purchase #3	$200.50	12.658%	$225.8793	$225.88	$225.90	$225.90
Purchase #4	$71.47	4.677%	$74.8127	$74.81	$74.80	$74.80
Purchase #5	$107.36	6.743%	$114.5993	$114.60	$114.60	$114.60
Purchase #6	$228.41	6.861%	$244.0812	$244.08	$244.10	$244.10
Purchase #7	$230.68	10.277%	$254.387	$254.39	$254.40	$254.40
7 purchase totals =	$1,151.35		$1,261.3056	$1,261.30	$1,261.30	$1,261.30