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	$144.95	5.686%	$153.1919	$153.19	$153.20	$153.20
Purchase #2	$56.78	13.660%	$64.5361	$64.54	$64.55	$64.50
Purchase #3	$166.98	10.472%	$184.4661	$184.47	$184.45	$184.50
Purchase #4	$160.47	6.150%	$170.3389	$170.34	$170.35	$170.30
Purchase #5	$240.53	6.591%	$256.3833	$256.38	$256.40	$256.40
Purchase #6	$27.61	4.264%	$28.7873	$28.79	$28.80	$28.80
Purchase #7	$170.90	7.567%	$183.832	$183.83	$183.85	$183.80
7 purchase totals =	$968.22		$1,041.5356	$1,041.54	$1,041.60	$1,041.50