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	$137.81	4.466%	$143.9646	$143.96	$143.95	$144.00
Purchase #2	$72.82	13.808%	$82.875	$82.88	$82.90	$82.90
Purchase #3	$40.77	10.618%	$45.099	$45.10	$45.10	$45.10
Purchase #4	$84.57	5.857%	$89.5233	$89.52	$89.50	$89.50
Purchase #5	$94.93	5.190%	$99.8569	$99.86	$99.85	$99.90
Purchase #6	$26.81	7.768%	$28.8926	$28.89	$28.90	$28.90
Purchase #7	$43.57	7.506%	$46.8404	$46.84	$46.85	$46.80
7 purchase totals =	$501.28		$537.0518	$537.05	$537.05	$537.10