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	$142.93	9.549%	$156.5784	$156.58	$156.60	$156.60
Purchase #2	$171.38	4.470%	$179.0407	$179.04	$179.05	$179.00
Purchase #3	$146.41	9.402%	$160.1755	$160.18	$160.20	$160.20
Purchase #4	$86.45	4.495%	$90.3359	$90.34	$90.35	$90.30
Purchase #5	$27.82	13.459%	$31.5643	$31.56	$31.55	$31.60
Purchase #6	$226.36	9.491%	$247.8438	$247.84	$247.85	$247.80
Purchase #7	$223.76	7.842%	$241.3073	$241.31	$241.30	$241.30
7 purchase totals =	$1,025.11		$1,106.8459	$1,106.85	$1,106.90	$1,106.80