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	$128.84	10.270%	$142.0719	$142.07	$142.05	$142.10
Purchase #2	$182.89	3.263%	$188.8577	$188.86	$188.85	$188.90
Purchase #3	$170.69	5.111%	$179.414	$179.41	$179.40	$179.40
Purchase #4	$40.39	6.658%	$43.0792	$43.08	$43.10	$43.10
Purchase #5	$212.79	4.524%	$222.4166	$222.42	$222.40	$222.40
Purchase #6	$198.38	3.652%	$205.6248	$205.62	$205.60	$205.60
Purchase #7	$183.80	12.792%	$207.3117	$207.31	$207.30	$207.30
7 purchase totals =	$1,117.78		$1,188.7759	$1,188.77	$1,188.70	$1,188.80