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	$39.72	6.420%	$42.27	$42.27	$42.25	$42.30
Purchase #2	$203.56	9.580%	$223.061	$223.06	$223.05	$223.10
Purchase #3	$98.89	8.264%	$107.0623	$107.06	$107.05	$107.10
Purchase #4	$153.62	11.669%	$171.5459	$171.55	$171.55	$171.50
Purchase #5	$192.66	5.169%	$202.6186	$202.62	$202.60	$202.60
Purchase #6	$205.71	4.252%	$214.4568	$214.46	$214.45	$214.50
Purchase #7	$78.92	9.632%	$86.5216	$86.52	$86.50	$86.50
7 purchase totals =	$973.08		$1,047.5362	$1,047.54	$1,047.45	$1,047.60