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	$94.98	10.313%	$104.7753	$104.78	$104.80	$104.80
Purchase #2	$37.54	6.745%	$40.0721	$40.07	$40.05	$40.10
Purchase #3	$190.64	10.846%	$211.3168	$211.32	$211.30	$211.30
Purchase #4	$41.31	6.156%	$43.853	$43.85	$43.85	$43.90
Purchase #5	$68.90	3.697%	$71.4472	$71.45	$71.45	$71.40
Purchase #6	$111.74	10.267%	$123.2123	$123.21	$123.20	$123.20
Purchase #7	$174.30	9.740%	$191.2768	$191.28	$191.30	$191.30
7 purchase totals =	$719.41		$785.9535	$785.96	$785.95	$786.00