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	$136.47	13.254%	$154.5577	$154.56	$154.55	$154.60
Purchase #2	$205.46	3.266%	$212.1703	$212.17	$212.15	$212.20
Purchase #3	$212.86	9.730%	$233.5713	$233.57	$233.55	$233.60
Purchase #4	$6.67	8.365%	$7.2279	$7.23	$7.25	$7.20
Purchase #5	$58.79	6.762%	$62.7654	$62.77	$62.75	$62.80
Purchase #6	$180.93	5.228%	$190.389	$190.39	$190.40	$190.40
Purchase #7	$150.85	3.628%	$156.3228	$156.32	$156.30	$156.30
7 purchase totals =	$952.03		$1,017.0044	$1,017.01	$1,016.95	$1,017.10