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	$205.47	6.650%	$219.1338	$219.13	$219.15	$219.10
Purchase #2	$198.61	8.851%	$216.189	$216.19	$216.20	$216.20
Purchase #3	$38.27	3.789%	$39.7201	$39.72	$39.70	$39.70
Purchase #4	$150.60	6.656%	$160.6239	$160.62	$160.60	$160.60
Purchase #5	$171.91	4.491%	$179.6305	$179.63	$179.65	$179.60
Purchase #6	$63.66	11.212%	$70.7976	$70.80	$70.80	$70.80
Purchase #7	$94.31	6.479%	$100.4203	$100.42	$100.40	$100.40
7 purchase totals =	$922.83		$986.5152	$986.51	$986.50	$986.40