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	$184.72	6.517%	$196.7582	$196.76	$196.75	$196.80
Purchase #2	$206.66	9.172%	$225.6149	$225.61	$225.60	$225.60
Purchase #3	$152.49	7.785%	$164.3613	$164.36	$164.35	$164.40
Purchase #4	$55.54	7.773%	$59.8571	$59.86	$59.85	$59.90
Purchase #5	$205.47	3.773%	$213.2224	$213.22	$213.20	$213.20
Purchase #6	$245.85	9.424%	$269.0189	$269.02	$269.00	$269.00
Purchase #7	$152.52	3.346%	$157.6233	$157.62	$157.60	$157.60
7 purchase totals =	$1,203.25		$1,286.4561	$1,286.45	$1,286.35	$1,286.50