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	$231.91	6.735%	$247.5291	$247.53	$247.55	$247.50
Purchase #2	$74.37	8.359%	$80.5866	$80.59	$80.60	$80.60
Purchase #3	$86.40	4.664%	$90.4297	$90.43	$90.45	$90.40
Purchase #4	$28.69	9.360%	$31.3754	$31.38	$31.40	$31.40
Purchase #5	$106.25	9.507%	$116.3512	$116.35	$116.35	$116.40
Purchase #6	$54.53	9.364%	$59.6362	$59.64	$59.65	$59.60
Purchase #7	$239.58	7.498%	$257.5437	$257.54	$257.55	$257.50
7 purchase totals =	$821.73		$883.4519	$883.46	$883.55	$883.40