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	$169.73	9.517%	$185.8832	$185.88	$185.90	$185.90
Purchase #2	$79.66	3.856%	$82.7317	$82.73	$82.75	$82.70
Purchase #3	$42.66	8.611%	$46.3335	$46.33	$46.35	$46.30
Purchase #4	$169.41	6.538%	$180.486	$180.49	$180.50	$180.50
Purchase #5	$181.89	3.255%	$187.8105	$187.81	$187.80	$187.80
Purchase #6	$213.52	6.200%	$226.7582	$226.76	$226.75	$226.80
Purchase #7	$152.89	9.632%	$167.6164	$167.62	$167.60	$167.60
7 purchase totals =	$1,009.76		$1,077.6195	$1,077.62	$1,077.65	$1,077.60