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	$236.25	13.160%	$267.3405	$267.34	$267.35	$267.30
Purchase #2	$165.35	10.708%	$183.0557	$183.06	$183.05	$183.10
Purchase #3	$104.81	6.714%	$111.8469	$111.85	$111.85	$111.80
Purchase #4	$76.88	11.683%	$85.8619	$85.86	$85.85	$85.90
Purchase #5	$61.36	10.744%	$67.9525	$67.95	$67.95	$68.00
Purchase #6	$87.95	13.245%	$99.599	$99.60	$99.60	$99.60
Purchase #7	$178.72	9.528%	$195.7484	$195.75	$195.75	$195.70
7 purchase totals =	$911.32		$1,011.4049	$1,011.41	$1,011.40	$1,011.40