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	$51.51	5.695%	$54.4435	$54.44	$54.45	$54.40
Purchase #2	$123.32	12.312%	$138.5032	$138.50	$138.50	$138.50
Purchase #3	$212.62	6.228%	$225.862	$225.86	$225.85	$225.90
Purchase #4	$85.77	8.160%	$92.7688	$92.77	$92.75	$92.80
Purchase #5	$125.41	13.566%	$142.4231	$142.42	$142.40	$142.40
Purchase #6	$198.91	3.357%	$205.5874	$205.59	$205.60	$205.60
Purchase #7	$149.25	7.731%	$160.7885	$160.79	$160.80	$160.80
7 purchase totals =	$946.79		$1,020.3765	$1,020.37	$1,020.35	$1,020.40