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	$146.81	7.846%	$158.3287	$158.33	$158.35	$158.30
Purchase #2	$140.39	5.112%	$147.5667	$147.57	$147.55	$147.60
Purchase #3	$168.53	6.237%	$179.0412	$179.04	$179.05	$179.00
Purchase #4	$148.97	10.660%	$164.8502	$164.85	$164.85	$164.90
Purchase #5	$115.44	3.267%	$119.2114	$119.21	$119.20	$119.20
Purchase #6	$222.56	10.736%	$246.454	$246.45	$246.45	$246.50
Purchase #7	$54.96	12.851%	$62.0229	$62.02	$62.00	$62.00
7 purchase totals =	$997.66		$1,077.4751	$1,077.47	$1,077.45	$1,077.50