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	$176.45	4.866%	$185.0361	$185.04	$185.05	$185.00
Purchase #2	$149.80	7.124%	$160.4718	$160.47	$160.45	$160.50
Purchase #3	$147.67	6.447%	$157.1903	$157.19	$157.20	$157.20
Purchase #4	$128.69	3.726%	$133.485	$133.49	$133.50	$133.50
Purchase #5	$27.81	13.632%	$31.6011	$31.60	$31.60	$31.60
Purchase #6	$148.30	12.836%	$167.3358	$167.34	$167.35	$167.30
Purchase #7	$37.88	11.793%	$42.3472	$42.35	$42.35	$42.30
7 purchase totals =	$816.60		$877.4673	$877.48	$877.50	$877.40