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	$45.48	4.188%	$47.3847	$47.38	$47.40	$47.40
Purchase #2	$149.60	3.158%	$154.3244	$154.32	$154.30	$154.30
Purchase #3	$135.74	4.537%	$141.8985	$141.90	$141.90	$141.90
Purchase #4	$23.34	8.755%	$25.3834	$25.38	$25.40	$25.40
Purchase #5	$89.51	3.279%	$92.445	$92.45	$92.45	$92.40
Purchase #6	$56.92	10.533%	$62.9154	$62.92	$62.90	$62.90
Purchase #7	$54.75	13.538%	$62.1621	$62.16	$62.15	$62.20
7 purchase totals =	$555.34		$586.5135	$586.51	$586.50	$586.50