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	$240.41	7.111%	$257.5056	$257.51	$257.50	$257.50
Purchase #2	$107.34	6.248%	$114.0466	$114.05	$114.05	$114.00
Purchase #3	$179.58	10.467%	$198.3766	$198.38	$198.40	$198.40
Purchase #4	$35.47	10.393%	$39.1564	$39.16	$39.15	$39.20
Purchase #5	$181.76	9.736%	$199.4562	$199.46	$199.45	$199.50
Purchase #6	$194.93	11.586%	$217.5146	$217.51	$217.50	$217.50
Purchase #7	$128.58	6.123%	$136.453	$136.45	$136.45	$136.50
7 purchase totals =	$1,068.07		$1,162.5090	$1,162.52	$1,162.50	$1,162.60