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	$44.34	3.467%	$45.8773	$45.88	$45.90	$45.90
Purchase #2	$100.93	3.588%	$104.5514	$104.55	$104.55	$104.60
Purchase #3	$155.69	5.432%	$164.1471	$164.15	$164.15	$164.10
Purchase #4	$217.54	12.746%	$245.2676	$245.27	$245.25	$245.30
Purchase #5	$42.79	6.565%	$45.5992	$45.60	$45.60	$45.60
Purchase #6	$124.96	5.457%	$131.7791	$131.78	$131.80	$131.80
Purchase #7	$41.89	5.559%	$44.2187	$44.22	$44.20	$44.20
7 purchase totals =	$728.14		$781.4404	$781.45	$781.45	$781.50