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	$167.34	5.868%	$177.1595	$177.16	$177.15	$177.20
Purchase #2	$192.66	4.172%	$200.6978	$200.70	$200.70	$200.70
Purchase #3	$102.89	3.570%	$106.5632	$106.56	$106.55	$106.60
Purchase #4	$82.60	10.742%	$91.4729	$91.47	$91.45	$91.50
Purchase #5	$164.64	10.175%	$181.3921	$181.39	$181.40	$181.40
Purchase #6	$126.37	3.127%	$130.3216	$130.32	$130.30	$130.30
Purchase #7	$81.50	9.232%	$89.0241	$89.02	$89.00	$89.00
7 purchase totals =	$918.00		$976.6312	$976.62	$976.55	$976.70