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	$38.90	11.723%	$43.4602	$43.46	$43.45	$43.50
Purchase #2	$246.59	4.298%	$257.1884	$257.19	$257.20	$257.20
Purchase #3	$107.67	5.468%	$113.5574	$113.56	$113.55	$113.60
Purchase #4	$79.75	13.865%	$90.8073	$90.81	$90.80	$90.80
Purchase #5	$78.58	6.544%	$83.7223	$83.72	$83.70	$83.70
Purchase #6	$226.77	12.109%	$254.2296	$254.23	$254.25	$254.20
Purchase #7	$250.94	6.635%	$267.5899	$267.59	$267.60	$267.60
7 purchase totals =	$1,029.20		$1,110.5551	$1,110.56	$1,110.55	$1,110.60