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	$137.64	6.231%	$146.2163	$146.22	$146.20	$146.20
Purchase #2	$18.94	12.173%	$21.2456	$21.25	$21.25	$21.20
Purchase #3	$183.61	9.220%	$200.5388	$200.54	$200.55	$200.50
Purchase #4	$224.29	7.874%	$241.9506	$241.95	$241.95	$242.00
Purchase #5	$19.33	10.214%	$21.3044	$21.30	$21.30	$21.30
Purchase #6	$53.42	11.443%	$59.5329	$59.53	$59.55	$59.50
Purchase #7	$63.69	10.264%	$70.2271	$70.23	$70.25	$70.20
7 purchase totals =	$700.92		$761.0157	$761.02	$761.05	$760.90