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	$191.37	4.664%	$200.2955	$200.30	$200.30	$200.30
Purchase #2	$91.75	6.312%	$97.5413	$97.54	$97.55	$97.50
Purchase #3	$120.87	13.860%	$137.6226	$137.62	$137.60	$137.60
Purchase #4	$111.53	5.622%	$117.8002	$117.80	$117.80	$117.80
Purchase #5	$220.81	7.852%	$238.148	$238.15	$238.15	$238.10
Purchase #6	$102.70	9.583%	$112.5417	$112.54	$112.55	$112.50
Purchase #7	$239.98	13.155%	$271.5494	$271.55	$271.55	$271.50
7 purchase totals =	$1,079.01		$1,175.4987	$1,175.50	$1,175.50	$1,175.30