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	6.739%	$146.9156	$146.92	$146.90	$146.90
Purchase #2	$14.43	7.105%	$15.4553	$15.46	$15.45	$15.50
Purchase #3	$128.96	9.469%	$141.1712	$141.17	$141.15	$141.20
Purchase #4	$194.33	8.794%	$211.4194	$211.42	$211.40	$211.40
Purchase #5	$179.88	9.136%	$196.3138	$196.31	$196.30	$196.30
Purchase #6	$206.29	3.699%	$213.9207	$213.92	$213.90	$213.90
Purchase #7	$186.76	3.730%	$193.7261	$193.73	$193.75	$193.70
7 purchase totals =	$1,048.29		$1,118.9221	$1,118.93	$1,118.85	$1,118.90