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	$244.84	7.658%	$263.5898	$263.59	$263.60	$263.60
Purchase #2	$205.94	10.198%	$226.9418	$226.94	$226.95	$226.90
Purchase #3	$123.76	7.731%	$133.3279	$133.33	$133.35	$133.30
Purchase #4	$59.83	12.733%	$67.4482	$67.45	$67.45	$67.40
Purchase #5	$177.98	4.444%	$185.8894	$185.89	$185.90	$185.90
Purchase #6	$95.39	7.228%	$102.2848	$102.28	$102.30	$102.30
Purchase #7	$91.94	5.504%	$97.0004	$97.00	$97.00	$97.00
7 purchase totals =	$999.68		$1,076.4823	$1,076.48	$1,076.55	$1,076.40