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	$194.52	8.812%	$211.6611	$211.66	$211.65	$211.70
Purchase #2	$59.90	4.421%	$62.5482	$62.55	$62.55	$62.50
Purchase #3	$82.85	8.606%	$89.9801	$89.98	$90.00	$90.00
Purchase #4	$177.83	6.574%	$189.5205	$189.52	$189.50	$189.50
Purchase #5	$245.38	12.223%	$275.3728	$275.37	$275.35	$275.40
Purchase #6	$241.82	12.382%	$271.7622	$271.76	$271.75	$271.80
Purchase #7	$171.61	7.272%	$184.0895	$184.09	$184.10	$184.10
7 purchase totals =	$1,173.91		$1,284.9344	$1,284.93	$1,284.90	$1,285.00