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	$142.54	5.585%	$150.5009	$150.50	$150.50	$150.50
Purchase #2	$148.60	12.301%	$166.8793	$166.88	$166.90	$166.90
Purchase #3	$139.89	5.401%	$147.4455	$147.45	$147.45	$147.40
Purchase #4	$139.42	13.870%	$158.7576	$158.76	$158.75	$158.80
Purchase #5	$202.36	13.799%	$230.2837	$230.28	$230.30	$230.30
Purchase #6	$217.52	12.870%	$245.5148	$245.51	$245.50	$245.50
Purchase #7	$31.55	6.457%	$33.5872	$33.59	$33.60	$33.60
7 purchase totals =	$1,021.88		$1,132.9690	$1,132.97	$1,133.00	$1,133.00