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	$51.52	8.421%	$55.8585	$55.86	$55.85	$55.90
Purchase #2	$27.71	11.873%	$31	$31.00	$31.00	$31.00
Purchase #3	$93.27	11.839%	$104.3122	$104.31	$104.30	$104.30
Purchase #4	$180.29	9.740%	$197.8502	$197.85	$197.85	$197.90
Purchase #5	$101.50	9.874%	$111.5221	$111.52	$111.50	$111.50
Purchase #6	$137.97	5.312%	$145.299	$145.30	$145.30	$145.30
Purchase #7	$155.92	9.514%	$170.7542	$170.75	$170.75	$170.80
7 purchase totals =	$748.18		$816.5962	$816.59	$816.55	$816.70