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	$92.54	4.729%	$96.9162	$96.92	$96.90	$96.90
Purchase #2	$109.78	6.513%	$116.93	$116.93	$116.95	$116.90
Purchase #3	$187.66	3.839%	$194.8643	$194.86	$194.85	$194.90
Purchase #4	$236.32	9.185%	$258.026	$258.03	$258.05	$258.00
Purchase #5	$155.49	7.280%	$166.8097	$166.81	$166.80	$166.80
Purchase #6	$249.84	8.185%	$270.2894	$270.29	$270.30	$270.30
Purchase #7	$19.27	4.233%	$20.0857	$20.09	$20.10	$20.10
7 purchase totals =	$1,050.90		$1,123.9213	$1,123.93	$1,123.95	$1,123.90