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	$134.52	7.486%	$144.5902	$144.59	$144.60	$144.60
Purchase #2	$162.26	13.723%	$184.5269	$184.53	$184.55	$184.50
Purchase #3	$153.66	8.410%	$166.5828	$166.58	$166.60	$166.60
Purchase #4	$213.86	6.681%	$228.148	$228.15	$228.15	$228.10
Purchase #5	$67.73	4.229%	$70.5943	$70.59	$70.60	$70.60
Purchase #6	$183.56	12.427%	$206.371	$206.37	$206.35	$206.40
Purchase #7	$150.53	10.661%	$166.578	$166.58	$166.60	$166.60
7 purchase totals =	$1,066.12		$1,167.3912	$1,167.39	$1,167.45	$1,167.40