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	$175.82	11.864%	$196.6793	$196.68	$196.70	$196.70
Purchase #2	$227.86	4.541%	$238.2071	$238.21	$238.20	$238.20
Purchase #3	$51.40	6.633%	$54.8094	$54.81	$54.80	$54.80
Purchase #4	$81.52	9.569%	$89.3206	$89.32	$89.30	$89.30
Purchase #5	$206.93	5.144%	$217.5745	$217.57	$217.55	$217.60
Purchase #6	$88.85	11.571%	$99.1308	$99.13	$99.15	$99.10
Purchase #7	$175.69	4.498%	$183.5925	$183.59	$183.60	$183.60
7 purchase totals =	$1,008.07		$1,079.3142	$1,079.31	$1,079.30	$1,079.30