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	$227.84	6.226%	$242.0253	$242.03	$242.05	$242.00
Purchase #2	$48.81	5.593%	$51.5399	$51.54	$51.55	$51.50
Purchase #3	$78.40	6.208%	$83.2671	$83.27	$83.25	$83.30
Purchase #4	$147.60	3.596%	$152.9077	$152.91	$152.90	$152.90
Purchase #5	$209.48	5.647%	$221.3093	$221.31	$221.30	$221.30
Purchase #6	$131.86	3.834%	$136.9155	$136.92	$136.90	$136.90
Purchase #7	$123.30	12.436%	$138.6336	$138.63	$138.65	$138.60
7 purchase totals =	$967.29		$1,026.5984	$1,026.61	$1,026.60	$1,026.50