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	$241.76	10.407%	$266.92	$266.92	$266.90	$266.90
Purchase #2	$80.85	12.371%	$90.852	$90.85	$90.85	$90.90
Purchase #3	$183.63	7.181%	$196.8165	$196.82	$196.80	$196.80
Purchase #4	$141.38	6.411%	$150.4439	$150.44	$150.45	$150.40
Purchase #5	$230.38	6.279%	$244.8456	$244.85	$244.85	$244.80
Purchase #6	$91.43	12.225%	$102.6073	$102.61	$102.60	$102.60
Purchase #7	$30.34	11.687%	$33.8858	$33.89	$33.90	$33.90
7 purchase totals =	$999.77		$1,086.3711	$1,086.38	$1,086.35	$1,086.30