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	$175.91	12.270%	$197.4942	$197.49	$197.50	$197.50
Purchase #2	$139.73	3.416%	$144.5032	$144.50	$144.50	$144.50
Purchase #3	$107.66	4.798%	$112.8255	$112.83	$112.85	$112.80
Purchase #4	$134.98	12.654%	$152.0604	$152.06	$152.05	$152.10
Purchase #5	$133.95	13.407%	$151.9087	$151.91	$151.90	$151.90
Purchase #6	$193.42	9.661%	$212.1063	$212.11	$212.10	$212.10
Purchase #7	$128.96	8.466%	$139.8778	$139.88	$139.90	$139.90
7 purchase totals =	$1,014.61		$1,110.7761	$1,110.78	$1,110.80	$1,110.80