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	$221.86	13.632%	$252.104	$252.10	$252.10	$252.10
Purchase #2	$123.47	3.646%	$127.9717	$127.97	$127.95	$128.00
Purchase #3	$211.71	12.596%	$238.377	$238.38	$238.40	$238.40
Purchase #4	$98.81	6.866%	$105.5943	$105.59	$105.60	$105.60
Purchase #5	$75.43	6.670%	$80.4612	$80.46	$80.45	$80.50
Purchase #6	$154.84	9.736%	$169.9152	$169.92	$169.90	$169.90
Purchase #7	$76.73	12.320%	$86.1831	$86.18	$86.20	$86.20
7 purchase totals =	$962.85		$1,060.6065	$1,060.60	$1,060.60	$1,060.70