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	$176.47	4.570%	$184.5347	$184.53	$184.55	$184.50
Purchase #2	$238.41	4.794%	$249.8394	$249.84	$249.85	$249.80
Purchase #3	$164.37	8.498%	$178.3382	$178.34	$178.35	$178.30
Purchase #4	$68.59	13.802%	$78.0568	$78.06	$78.05	$78.10
Purchase #5	$107.38	3.816%	$111.4776	$111.48	$111.50	$111.50
Purchase #6	$103.98	4.229%	$108.3773	$108.38	$108.40	$108.40
Purchase #7	$241.34	13.339%	$273.5323	$273.53	$273.55	$273.50
7 purchase totals =	$1,100.54		$1,184.1563	$1,184.16	$1,184.25	$1,184.10