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	$48.90	13.381%	$55.4433	$55.44	$55.45	$55.40
Purchase #2	$185.81	4.594%	$194.3461	$194.35	$194.35	$194.30
Purchase #3	$90.55	6.655%	$96.5761	$96.58	$96.60	$96.60
Purchase #4	$91.94	9.792%	$100.9428	$100.94	$100.95	$100.90
Purchase #5	$92.26	13.600%	$104.8074	$104.81	$104.80	$104.80
Purchase #6	$34.45	8.585%	$37.4075	$37.41	$37.40	$37.40
Purchase #7	$130.26	13.866%	$148.3219	$148.32	$148.30	$148.30
7 purchase totals =	$674.17		$737.8451	$737.85	$737.85	$737.70