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	$67.31	11.791%	$75.2465	$75.25	$75.25	$75.20
Purchase #2	$222.72	9.674%	$244.2659	$244.27	$244.25	$244.30
Purchase #3	$150.42	9.658%	$164.9476	$164.95	$164.95	$164.90
Purchase #4	$148.69	13.630%	$168.9564	$168.96	$168.95	$169.00
Purchase #5	$155.54	5.656%	$164.3373	$164.34	$164.35	$164.30
Purchase #6	$38.40	13.601%	$43.6228	$43.62	$43.60	$43.60
Purchase #7	$240.37	12.418%	$270.2191	$270.22	$270.20	$270.20
7 purchase totals =	$1,023.45		$1,131.5956	$1,131.61	$1,131.55	$1,131.50