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	$108.35	3.157%	$111.7706	$111.77	$111.75	$111.80
Purchase #2	$217.47	12.207%	$244.0166	$244.02	$244.00	$244.00
Purchase #3	$179.85	3.223%	$185.6466	$185.65	$185.65	$185.60
Purchase #4	$22.52	4.459%	$23.5242	$23.52	$23.50	$23.50
Purchase #5	$104.44	4.249%	$108.8777	$108.88	$108.90	$108.90
Purchase #6	$178.33	10.137%	$196.4073	$196.41	$196.40	$196.40
Purchase #7	$193.37	11.686%	$215.9672	$215.97	$215.95	$216.00
7 purchase totals =	$1,004.33		$1,086.2102	$1,086.22	$1,086.15	$1,086.20