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	$163.48	12.209%	$183.4393	$183.44	$183.45	$183.40
Purchase #2	$141.48	3.557%	$146.5124	$146.51	$146.50	$146.50
Purchase #3	$83.68	10.520%	$92.4831	$92.48	$92.50	$92.50
Purchase #4	$104.83	6.364%	$111.5014	$111.50	$111.50	$111.50
Purchase #5	$72.58	7.130%	$77.755	$77.76	$77.75	$77.80
Purchase #6	$127.80	12.737%	$144.0779	$144.08	$144.10	$144.10
Purchase #7	$248.28	13.285%	$281.264	$281.26	$281.25	$281.30
7 purchase totals =	$942.13		$1,037.0331	$1,037.03	$1,037.05	$1,037.10