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	$174.54	4.193%	$181.8585	$181.86	$181.85	$181.90
Purchase #2	$249.66	8.698%	$271.3754	$271.38	$271.40	$271.40
Purchase #3	$52.39	3.180%	$54.056	$54.06	$54.05	$54.10
Purchase #4	$218.89	7.724%	$235.7971	$235.80	$235.80	$235.80
Purchase #5	$212.57	13.492%	$241.2499	$241.25	$241.25	$241.20
Purchase #6	$138.35	10.379%	$152.7093	$152.71	$152.70	$152.70
Purchase #7	$243.66	12.792%	$274.829	$274.83	$274.85	$274.80
7 purchase totals =	$1,290.06		$1,411.8752	$1,411.89	$1,411.90	$1,411.90