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	$97.83	11.428%	$109.01	$109.01	$109.00	$109.00
Purchase #2	$72.96	12.250%	$81.8976	$81.90	$81.90	$81.90
Purchase #3	$200.69	7.737%	$216.2174	$216.22	$216.20	$216.20
Purchase #4	$35.72	12.849%	$40.3097	$40.31	$40.30	$40.30
Purchase #5	$127.34	13.446%	$144.4621	$144.46	$144.45	$144.50
Purchase #6	$212.86	6.549%	$226.8002	$226.80	$226.80	$226.80
Purchase #7	$176.28	4.326%	$183.9059	$183.91	$183.90	$183.90
7 purchase totals =	$923.68		$1,002.6029	$1,002.61	$1,002.55	$1,002.60