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	$75.86	5.525%	$80.0513	$80.05	$80.05	$80.10
Purchase #2	$79.42	3.700%	$82.3585	$82.36	$82.35	$82.40
Purchase #3	$151.76	11.206%	$168.7662	$168.77	$168.75	$168.80
Purchase #4	$246.39	12.257%	$276.59	$276.59	$276.60	$276.60
Purchase #5	$211.50	7.182%	$226.6899	$226.69	$226.70	$226.70
Purchase #6	$95.66	4.857%	$100.3062	$100.31	$100.30	$100.30
Purchase #7	$183.56	8.253%	$198.7092	$198.71	$198.70	$198.70
7 purchase totals =	$1,044.15		$1,133.4713	$1,133.48	$1,133.45	$1,133.60