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	$200.81	6.276%	$213.4128	$213.41	$213.40	$213.40
Purchase #2	$150.90	13.721%	$171.605	$171.61	$171.60	$171.60
Purchase #3	$169.72	3.236%	$175.2121	$175.21	$175.20	$175.20
Purchase #4	$100.37	11.314%	$111.7259	$111.73	$111.75	$111.70
Purchase #5	$166.79	5.376%	$175.7566	$175.76	$175.75	$175.80
Purchase #6	$64.48	5.396%	$67.9593	$67.96	$67.95	$68.00
Purchase #7	$66.33	7.543%	$71.3333	$71.33	$71.35	$71.30
7 purchase totals =	$919.40		$987.0050	$987.01	$987.00	$987.00