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	$42.79	6.226%	$45.4541	$45.45	$45.45	$45.50
Purchase #2	$12.93	6.833%	$13.8135	$13.81	$13.80	$13.80
Purchase #3	$119.57	5.611%	$126.2791	$126.28	$126.30	$126.30
Purchase #4	$62.64	9.432%	$68.5482	$68.55	$68.55	$68.50
Purchase #5	$96.65	9.453%	$105.7863	$105.79	$105.80	$105.80
Purchase #6	$12.37	8.774%	$13.4553	$13.46	$13.45	$13.50
Purchase #7	$81.96	8.820%	$89.1889	$89.19	$89.20	$89.20
7 purchase totals =	$428.91		$462.5254	$462.53	$462.55	$462.60