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	$55.94	13.138%	$63.2894	$63.29	$63.30	$63.30
Purchase #2	$96.96	3.398%	$100.2547	$100.25	$100.25	$100.30
Purchase #3	$53.98	3.758%	$56.0086	$56.01	$56.00	$56.00
Purchase #4	$83.55	10.782%	$92.5584	$92.56	$92.55	$92.60
Purchase #5	$68.34	11.187%	$75.9852	$75.99	$76.00	$76.00
Purchase #6	$185.80	12.760%	$209.5081	$209.51	$209.50	$209.50
Purchase #7	$73.61	6.572%	$78.4476	$78.45	$78.45	$78.40
7 purchase totals =	$618.18		$676.0520	$676.06	$676.05	$676.10