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	$115.70	9.383%	$126.5561	$126.56	$126.55	$126.60
Purchase #2	$104.57	6.691%	$111.5668	$111.57	$111.55	$111.60
Purchase #3	$79.91	13.782%	$90.9232	$90.92	$90.90	$90.90
Purchase #4	$195.66	6.479%	$208.3368	$208.34	$208.35	$208.30
Purchase #5	$48.94	4.166%	$50.9788	$50.98	$51.00	$51.00
Purchase #6	$238.33	6.514%	$253.8548	$253.85	$253.85	$253.90
Purchase #7	$250.46	5.535%	$264.323	$264.32	$264.30	$264.30
7 purchase totals =	$1,033.57		$1,106.5395	$1,106.54	$1,106.50	$1,106.60